Series#

This page gives an overview of all public Series methods.

class polars.Series( name: str | ArrayLike | None = None, values: ArrayLike | None = None, dtype: PolarsDataType | None = None, *, strict: bool = True, nan_to_null: bool = False, )[source]

A Series represents a single column in a polars DataFrame.

Parameters:

namestr, default None

Name of the Series. Will be used as a column name when used in a DataFrame. When not specified, name is set to an empty string.

valuesArrayLike, default None

One-dimensional data in various forms. Supported are: Sequence, Series, pyarrow Array, and numpy ndarray.

dtypeDataType, default None

Data type of the resulting Series. If set to None (default), the data type is inferred from the values input. The strategy for data type inference depends on the strict parameter:

If strict is set to True (default), the inferred data type is equal to the first non-null value, or Null if all values are null.
If strict is set to False, the inferred data type is the supertype of the values, or Object if no supertype can be found. WARNING: A full pass over the values is required to determine the supertype.
If no values were passed, the resulting data type is Null.

strictbool, default True

Throw an error if any value does not exactly match the given or inferred data type. If set to False, values that do not match the data type are cast to that data type or, if casting is not possible, set to null instead.

nan_to_nullbool, default False

In case a numpy array is used to create this Series, indicate how to deal with np.nan values. (This parameter is a no-op on non-numpy data).

Examples

Constructing a Series by specifying name and values positionally:

>>> s = pl.Series("a", [1, 2, 3])
>>> s
shape: (3,)
Series: 'a' [i64]
[
        1
        2
        3
]

Notice that the dtype is automatically inferred as a polars Int64:

>>> s.dtype
Int64

Constructing a Series with a specific dtype:

>>> s2 = pl.Series("a", [1, 2, 3], dtype=pl.Float32)
>>> s2
shape: (3,)
Series: 'a' [f32]
[
    1.0
    2.0
    3.0
]

It is possible to construct a Series with values as the first positional argument. This syntax considered an anti-pattern, but it can be useful in certain scenarios. You must specify any other arguments through keywords.

>>> s3 = pl.Series([1, 2, 3])
>>> s3
shape: (3,)
Series: '' [i64]
[
        1
        2
        3
]

Methods:

`abs`	Compute absolute values.
`alias`	Rename the series.
`all`	Return whether all values in the column are `True`.
`any`	Return whether any of the values in the column are `True`.
`append`	Append a Series to this one.
`arccos`	Compute the element-wise value for the inverse cosine.
`arccosh`	Compute the element-wise value for the inverse hyperbolic cosine.
`arcsin`	Compute the element-wise value for the inverse sine.
`arcsinh`	Compute the element-wise value for the inverse hyperbolic sine.
`arctan`	Compute the element-wise value for the inverse tangent.
`arctanh`	Compute the element-wise value for the inverse hyperbolic tangent.
`arg_max`	Get the index of the maximal value.
`arg_min`	Get the index of the minimal value.
`arg_sort`	Get the index values that would sort this Series.
`arg_true`	Get index values where Boolean Series evaluate True.
`arg_unique`	Get unique index as Series.
`bottom_k`	Return the `k` smallest elements.
`cast`	Cast between data types.
`cbrt`	Compute the cube root of the elements.
`ceil`	Rounds up to the nearest integer value.
`chunk_lengths`	Get the length of each individual chunk.
`clear`	Create an empty copy of the current Series, with zero to 'n' elements.
`clip`	Set values outside the given boundaries to the boundary value.
`clone`	Create a copy of this Series.
`cos`	Compute the element-wise value for the cosine.
`cosh`	Compute the element-wise value for the hyperbolic cosine.
`cot`	Compute the element-wise value for the cotangent.
`count`	Return the number of non-null elements in the column.
`cum_count`	Return the cumulative count of the non-null values in the column.
`cum_max`	Get an array with the cumulative max computed at every element.
`cum_min`	Get an array with the cumulative min computed at every element.
`cum_prod`	Get an array with the cumulative product computed at every element.
`cum_sum`	Get an array with the cumulative sum computed at every element.
`cumulative_eval`	Run an expression over a sliding window that increases `1` slot every iteration.
`cut`	Bin continuous values into discrete categories.
`describe`	Quick summary statistics of a Series.
`diff`	Calculate the first discrete difference between shifted items.
`dot`	Compute the dot/inner product between two Series.
`drop_nans`	Drop all floating point NaN values.
`drop_nulls`	Drop all null values.
`entropy`	Computes the entropy.
`eq`	Method equivalent of operator expression `series == other`.
`eq_missing`	Method equivalent of equality operator `series == other` where `None == None`.
`equals`	Check whether the Series is equal to another Series.
`estimated_size`	Return an estimation of the total (heap) allocated size of the Series.
`ewm_mean`	Exponentially-weighted moving average.
`ewm_mean_by`	Calculate time-based exponentially weighted moving average.
`ewm_std`	Exponentially-weighted moving standard deviation.
`ewm_var`	Exponentially-weighted moving variance.
`exp`	Compute the exponential, element-wise.
`explode`	Explode a list Series.
`extend`	Extend the memory backed by this Series with the values from another.
`extend_constant`	Extremely fast method for extending the Series with 'n' copies of a value.
`fill_nan`	Fill floating point NaN value with a fill value.
`fill_null`	Fill null values using the specified value or strategy.
`filter`	Filter elements by a boolean mask.
`floor`	Rounds down to the nearest integer value.
`gather`	Take values by index.
`gather_every`	Take every nth value in the Series and return as new Series.
`ge`	Method equivalent of operator expression `series >= other`.
`get_chunks`	Get the chunks of this Series as a list of Series.
`gt`	Method equivalent of operator expression `series > other`.
`has_nulls`	Check whether the Series contains one or more null values.
`has_validity`	Check whether the Series contains one or more null values.
`hash`	Hash the Series.
`head`	Get the first `n` elements.
`hist`	Bin values into buckets and count their occurrences.
`implode`	Aggregate values into a list.
`interpolate`	Fill null values using interpolation.
`interpolate_by`	Fill null values using interpolation based on another column.
`is_between`	Get a boolean mask of the values that are between the given lower/upper bounds.
`is_duplicated`	Get mask of all duplicated values.
`is_empty`	Check if the Series is empty.
`is_finite`	Returns a boolean Series indicating which values are finite.
`is_first_distinct`	Return a boolean mask indicating the first occurrence of each distinct value.
`is_in`	Check if elements of this Series are in the other Series.
`is_infinite`	Returns a boolean Series indicating which values are infinite.
`is_last_distinct`	Return a boolean mask indicating the last occurrence of each distinct value.
`is_nan`	Returns a boolean Series indicating which values are not NaN.
`is_not_nan`	Returns a boolean Series indicating which values are not NaN.
`is_not_null`	Returns a boolean Series indicating which values are not null.
`is_null`	Returns a boolean Series indicating which values are null.
`is_sorted`	Check if the Series is sorted.
`is_unique`	Get mask of all unique values.
`item`	Return the Series as a scalar, or return the element at the given index.
`kurtosis`	Compute the kurtosis (Fisher or Pearson) of a dataset.
`le`	Method equivalent of operator expression `series <= other`.
`len`	Return the number of elements in the Series.
`limit`	Get the first `n` elements.
`log`	Compute the logarithm to a given base.
`log10`	Compute the base 10 logarithm of the input array, element-wise.
`log1p`	Compute the natural logarithm of the input array plus one, element-wise.
`lower_bound`	Return the lower bound of this Series' dtype as a unit Series.
`lt`	Method equivalent of operator expression `series < other`.
`map_elements`	Map a custom/user-defined function (UDF) over elements in this Series.
`max`	Get the maximum value in this Series.
`mean`	Reduce this Series to the mean value.
`median`	Get the median of this Series.
`min`	Get the minimal value in this Series.
`mode`	Compute the most occurring value(s).
`n_chunks`	Get the number of chunks that this Series contains.
`n_unique`	Count the number of unique values in this Series.
`nan_max`	Get maximum value, but propagate/poison encountered NaN values.
`nan_min`	Get minimum value, but propagate/poison encountered NaN values.
`ne`	Method equivalent of operator expression `series != other`.
`ne_missing`	Method equivalent of equality operator `series != other` where `None == None`.
`new_from_index`	Create a new Series filled with values from the given index.
`not_`	Negate a boolean Series.
`null_count`	Count the null values in this Series.
`pct_change`	Computes percentage change between values.
`peak_max`	Get a boolean mask of the local maximum peaks.
`peak_min`	Get a boolean mask of the local minimum peaks.
`pow`	Raise to the power of the given exponent.
`product`	Reduce this Series to the product value.
`qcut`	Bin continuous values into discrete categories based on their quantiles.
`quantile`	Get the quantile value of this Series.
`rank`	Assign ranks to data, dealing with ties appropriately.
`rechunk`	Create a single chunk of memory for this Series.
`reinterpret`	Reinterpret the underlying bits as a signed/unsigned integer.
`rename`	Rename this Series.
`replace`	Replace values by different values of the same data type.
`replace_strict`	Replace all values by different values.
`reshape`	Reshape this Series to a flat Series or an Array Series.
`reverse`	Return Series in reverse order.
`rle`	Compress the Series data using run-length encoding.
`rle_id`	Get a distinct integer ID for each run of identical values.
`rolling_map`	Compute a custom rolling window function.
`rolling_max`	Apply a rolling max (moving max) over the values in this array.
`rolling_mean`	Apply a rolling mean (moving mean) over the values in this array.
`rolling_median`	Compute a rolling median.
`rolling_min`	Apply a rolling min (moving min) over the values in this array.
`rolling_quantile`	Compute a rolling quantile.
`rolling_skew`	Compute a rolling skew.
`rolling_std`	Compute a rolling std dev.
`rolling_sum`	Apply a rolling sum (moving sum) over the values in this array.
`rolling_var`	Compute a rolling variance.
`round`	Round underlying floating point data by `decimals` digits.
`round_sig_figs`	Round to a number of significant figures.
`sample`	Sample from this Series.
`scatter`	Set values at the index locations.
`search_sorted`	Find indices where elements should be inserted to maintain order.
`set`	Set masked values.
`set_sorted`	Flags the Series as 'sorted'.
`shift`	Shift values by the given number of indices.
`shrink_dtype`	Shrink numeric columns to the minimal required datatype.
`shrink_to_fit`	Shrink Series memory usage.
`shuffle`	Shuffle the contents of this Series.
`sign`	Compute the element-wise indication of the sign.
`sin`	Compute the element-wise value for the sine.
`sinh`	Compute the element-wise value for the hyperbolic sine.
`skew`	Compute the sample skewness of a data set.
`slice`	Get a slice of this Series.
`sort`	Sort this Series.
`sqrt`	Compute the square root of the elements.
`std`	Get the standard deviation of this Series.
`sum`	Reduce this Series to the sum value.
`tail`	Get the last `n` elements.
`tan`	Compute the element-wise value for the tangent.
`tanh`	Compute the element-wise value for the hyperbolic tangent.
`to_arrow`	Return the underlying Arrow array.
`to_dummies`	Get dummy/indicator variables.
`to_frame`	Cast this Series to a DataFrame.
`to_init_repr`	Convert Series to instantiatable string representation.
`to_jax`	Convert this Series to a Jax Array.
`to_list`	Convert this Series to a Python list.
`to_numpy`	Convert this Series to a NumPy ndarray.
`to_pandas`	Convert this Series to a pandas Series.
`to_physical`	Cast to physical representation of the logical dtype.
`to_torch`	Convert this Series to a PyTorch Tensor.
`top_k`	Return the `k` largest elements.
`unique`	Get unique elements in series.
`unique_counts`	Return a count of the unique values in the order of appearance.
`upper_bound`	Return the upper bound of this Series' dtype as a unit Series.
`value_counts`	Count the occurrences of unique values.
`var`	Get variance of this Series.
`zip_with`	Take values from self or other based on the given mask.

Attributes:

`dtype`	Get the data type of this Series.
`flags`	Get flags that are set on the Series.
`name`	Get the name of this Series.
`plot`	Create a plot namespace.
`shape`	Shape of this Series.

abs() → Series[source]

Compute absolute values.

Same as abs(series).

Examples

>>> s = pl.Series([1, -2, -3])
>>> s.abs()
shape: (3,)
Series: '' [i64]
[
    1
    2
    3
]

alias(name: str) → Series[source]

Rename the series.

Parameters:

name: The new name.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.alias("b")
shape: (3,)
Series: 'b' [i64]
[
        1
        2
        3
]

all(*, ignore_nulls: bool = True) → bool | None[source]

Return whether all values in the column are True.

Only works on columns of data type Boolean.

Parameters:

ignore_nulls

Ignore null values (default).

If set to False, Kleene logic is used to deal with nulls: if the column contains any null values and no False values, the output is None.

Returns:

bool or None

Examples

>>> pl.Series([True, True]).all()
True
>>> pl.Series([False, True]).all()
False
>>> pl.Series([None, True]).all()
True

Enable Kleene logic by setting ignore_nulls=False.

>>> pl.Series([None, True]).all(ignore_nulls=False)  # Returns None

any(*, ignore_nulls: bool = True) → bool | None[source]

Return whether any of the values in the column are True.

Only works on columns of data type Boolean.

Parameters:

ignore_nulls

Ignore null values (default).

If set to False, Kleene logic is used to deal with nulls: if the column contains any null values and no True values, the output is None.

Returns:

bool or None

Examples

>>> pl.Series([True, False]).any()
True
>>> pl.Series([False, False]).any()
False
>>> pl.Series([None, False]).any()
False

Enable Kleene logic by setting ignore_nulls=False.

>>> pl.Series([None, False]).any(ignore_nulls=False)  # Returns None

append(other: Series) → Self[source]

Append a Series to this one.

The resulting series will consist of multiple chunks.

Parameters:

other: Series to append.

Warning

This method modifies the series in-place. The series is returned for convenience only.

See also

extend

Examples

>>> a = pl.Series("a", [1, 2, 3])
>>> b = pl.Series("b", [4, 5])
>>> a.append(b)
shape: (5,)
Series: 'a' [i64]
[
    1
    2
    3
    4
    5
]

The resulting series will consist of multiple chunks.

>>> a.n_chunks()
2

arccos() → Series[source]

Compute the element-wise value for the inverse cosine.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.arccos()
shape: (3,)
Series: 'a' [f64]
[
    0.0
    1.570796
    3.141593
]

arccosh() → Series[source]

Compute the element-wise value for the inverse hyperbolic cosine.

Examples

>>> s = pl.Series("a", [5.0, 1.0, 0.0, -1.0])
>>> s.arccosh()
shape: (4,)
Series: 'a' [f64]
[
    2.292432
    0.0
    NaN
    NaN
]

arcsin() → Series[source]

Compute the element-wise value for the inverse sine.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.arcsin()
shape: (3,)
Series: 'a' [f64]
[
    1.570796
    0.0
    -1.570796
]

arcsinh() → Series[source]

Compute the element-wise value for the inverse hyperbolic sine.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.arcsinh()
shape: (3,)
Series: 'a' [f64]
[
    0.881374
    0.0
    -0.881374
]

arctan() → Series[source]

Compute the element-wise value for the inverse tangent.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.arctan()
shape: (3,)
Series: 'a' [f64]
[
    0.785398
    0.0
    -0.785398
]

arctanh() → Series[source]

Compute the element-wise value for the inverse hyperbolic tangent.

Examples

>>> s = pl.Series("a", [2.0, 1.0, 0.5, 0.0, -0.5, -1.0, -1.1])
>>> s.arctanh()
shape: (7,)
Series: 'a' [f64]
[
    NaN
    inf
    0.549306
    0.0
    -0.549306
    -inf
    NaN
]

arg_max() → int | None[source]

Get the index of the maximal value.

Returns:

int

Examples

>>> s = pl.Series("a", [3, 2, 1])
>>> s.arg_max()
0

arg_min() → int | None[source]

Get the index of the minimal value.

Returns:

int

Examples

>>> s = pl.Series("a", [3, 2, 1])
>>> s.arg_min()
2

arg_sort( *, descending: bool = False, nulls_last: bool = False, ) → Series[source]

Get the index values that would sort this Series.

Parameters:

descending: Sort in descending order.
nulls_last: Place null values last instead of first.

See also

Series.gather: Take values by index.
Series.rank: Get the rank of each row.

Examples

>>> s = pl.Series("a", [5, 3, 4, 1, 2])
>>> s.arg_sort()
shape: (5,)
Series: 'a' [u32]
[
    3
    4
    1
    2
    0
]

arg_true() → Series[source]

Get index values where Boolean Series evaluate True.

Returns:

Series: Series of data type UInt32.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> (s == 2).arg_true()
shape: (1,)
Series: 'a' [u32]
[
        1
]

arg_unique() → Series[source]

Get unique index as Series.

Returns:

Series

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.arg_unique()
shape: (3,)
Series: 'a' [u32]
[
        0
        1
        3
]

bottom_k(k: int = 5) → Series[source]

Return the k smallest elements.

Non-null elements are always preferred over null elements. The output is not guaranteed to be in any particular order, call sort() after this function if you wish the output to be sorted. This has time complexity:

This has time complexity:

\[O(n)\]

Parameters:

k: Number of elements to return.

See also

top_k

Examples

>>> s = pl.Series("a", [2, 5, 1, 4, 3])
>>> s.bottom_k(3)
shape: (3,)
Series: 'a' [i64]
[
    1
    2
    3
]

cast( dtype: PolarsDataType | type[int] | type[float] | type[str] | type[bool], *, strict: bool = True, wrap_numerical: bool = False, ) → Self[source]

Cast between data types.

Parameters:

dtype: DataType to cast to.
strict: If True invalid casts generate exceptions instead of nulls.
wrap_numerical: If True numeric casts wrap overflowing values instead of marking the cast as invalid.

Examples

>>> s = pl.Series("a", [True, False, True])
>>> s
shape: (3,)
Series: 'a' [bool]
[
    true
    false
    true
]

>>> s.cast(pl.UInt32)
shape: (3,)
Series: 'a' [u32]
[
    1
    0
    1
]

cbrt() → Series[source]

Compute the cube root of the elements.

Optimization for

>>> pl.Series([1, 2]) ** (1.0 / 3)
shape: (2,)
Series: '' [f64]
[
    1.0
    1.259921
]

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.cbrt()
shape: (3,)
Series: '' [f64]
[
    1.0
    1.259921
    1.44225
]

ceil() → Series[source]

Rounds up to the nearest integer value.

Only works on floating point Series.

Examples

>>> s = pl.Series("a", [1.12345, 2.56789, 3.901234])
>>> s.ceil()
shape: (3,)
Series: 'a' [f64]
[
        2.0
        3.0
        4.0
]

chunk_lengths() → list[int][source]

Get the length of each individual chunk.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s2 = pl.Series("a", [4, 5, 6])

Concatenate Series with rechunk = True

>>> pl.concat([s, s2], rechunk=True).chunk_lengths()
[6]

Concatenate Series with rechunk = False

>>> pl.concat([s, s2], rechunk=False).chunk_lengths()
[3, 3]

clear(n: int = 0) → Series[source]

Create an empty copy of the current Series, with zero to ‘n’ elements.

The copy has an identical name/dtype, but no data.

Parameters:

n: Number of (empty) elements to return in the cleared frame.

See also

clone: Cheap deepcopy/clone.

Examples

>>> s = pl.Series("a", [None, True, False])
>>> s.clear()
shape: (0,)
Series: 'a' [bool]
[
]

>>> s.clear(n=2)
shape: (2,)
Series: 'a' [bool]
[
    null
    null
]

Set values outside the given boundaries to the boundary value.

Parameters:

lower_bound: Lower bound. Accepts expression input. Non-expression inputs are parsed as literals. If set to None (default), no lower bound is applied.
upper_bound: Upper bound. Accepts expression input. Non-expression inputs are parsed as literals. If set to None (default), no upper bound is applied.

See also

when

Notes

This method only works for numeric and temporal columns. To clip other data types, consider writing a when-then-otherwise expression. See when().

Examples

Specifying both a lower and upper bound:

>>> s = pl.Series([-50, 5, 50, None])
>>> s.clip(1, 10)
shape: (4,)
Series: '' [i64]
[
        1
        5
        10
        null
]

Specifying only a single bound:

>>> s.clip(upper_bound=10)
shape: (4,)
Series: '' [i64]
[
        -50
        5
        10
        null
]

clone() → Self[source]

Create a copy of this Series.

This is a cheap operation that does not copy data.

See also

clear: Create an empty copy of the current Series, with identical schema but no data.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.clone()
shape: (3,)
Series: 'a' [i64]
[
        1
        2
        3
]

cos() → Series[source]

Compute the element-wise value for the cosine.

Examples

>>> import math
>>> s = pl.Series("a", [0.0, math.pi / 2.0, math.pi])
>>> s.cos()
shape: (3,)
Series: 'a' [f64]
[
    1.0
    6.1232e-17
    -1.0
]

cosh() → Series[source]

Compute the element-wise value for the hyperbolic cosine.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.cosh()
shape: (3,)
Series: 'a' [f64]
[
    1.543081
    1.0
    1.543081
]

cot() → Series[source]

Compute the element-wise value for the cotangent.

Examples

>>> import math
>>> s = pl.Series("a", [0.0, math.pi / 2.0, math.pi])
>>> s.cot()
shape: (3,)
Series: 'a' [f64]
[
    inf
    6.1232e-17
    -8.1656e15
]

count() → int[source]

Return the number of non-null elements in the column.

See also

len

Examples

>>> s = pl.Series("a", [1, 2, None])
>>> s.count()
2

cum_count(*, reverse: bool = False) → Self[source]

Return the cumulative count of the non-null values in the column.

Parameters:

reverse: Reverse the operation.

Examples

>>> s = pl.Series(["x", "k", None, "d"])
>>> s.cum_count()
shape: (4,)
Series: '' [u32]
[
        1
        2
        2
        3
]

cum_max(*, reverse: bool = False) → Series[source]

Get an array with the cumulative max computed at every element.

Parameters:

reverse: reverse the operation.

Examples

>>> s = pl.Series("s", [3, 5, 1])
>>> s.cum_max()
shape: (3,)
Series: 's' [i64]
[
    3
    5
    5
]

cum_min(*, reverse: bool = False) → Series[source]

Get an array with the cumulative min computed at every element.

Parameters:

reverse: reverse the operation.

Examples

>>> s = pl.Series("s", [1, 2, 3])
>>> s.cum_min()
shape: (3,)
Series: 's' [i64]
[
    1
    1
    1
]

cum_prod(*, reverse: bool = False) → Series[source]

Get an array with the cumulative product computed at every element.

Parameters:

reverse: reverse the operation.

Notes

Dtypes in {Int8, UInt8, Int16, UInt16} are cast to Int64 before summing to prevent overflow issues.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.cum_prod()
shape: (3,)
Series: 'a' [i64]
[
    1
    2
    6
]

cum_sum(*, reverse: bool = False) → Series[source]

Get an array with the cumulative sum computed at every element.

Parameters:

reverse: reverse the operation.

Notes

Dtypes in {Int8, UInt8, Int16, UInt16} are cast to Int64 before summing to prevent overflow issues.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.cum_sum()
shape: (3,)
Series: 'a' [i64]
[
    1
    3
    6
]

cumulative_eval( expr: Expr, *, min_periods: int = 1, parallel: bool = False, ) → Series[source]

Run an expression over a sliding window that increases 1 slot every iteration.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

expr: Expression to evaluate
min_periods: Number of valid values there should be in the window before the expression is evaluated. valid values = length - null_count
parallel: Run in parallel. Don’t do this in a group by or another operation that already has much parallelization.

Warning

This can be really slow as it can have O(n^2) complexity. Don’t use this for operations that visit all elements.

Examples

>>> s = pl.Series("values", [1, 2, 3, 4, 5])
>>> s.cumulative_eval(pl.element().first() - pl.element().last() ** 2)
shape: (5,)
Series: 'values' [i64]
[
    0
    -3
    -8
    -15
    -24
]

cut( breaks: Sequence[float], *, labels: Sequence[str] | None = None, left_closed: bool = False, include_breaks: bool = False, ) → Series[source]

Bin continuous values into discrete categories.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

breaks: List of unique cut points.
labels: Names of the categories. The number of labels must be equal to the number of cut points plus one.
left_closed: Set the intervals to be left-closed instead of right-closed.
include_breaks: Include a column with the right endpoint of the bin each observation falls in. This will change the data type of the output from a Categorical to a Struct.

Returns:

Series: Series of data type Categorical if include_breaks is set to False (default), otherwise a Series of data type Struct.

See also

qcut

Examples

Divide the column into three categories.

>>> s = pl.Series("foo", [-2, -1, 0, 1, 2])
>>> s.cut([-1, 1], labels=["a", "b", "c"])
shape: (5,)
Series: 'foo' [cat]
[
        "a"
        "a"
        "b"
        "b"
        "c"
]

Create a DataFrame with the breakpoint and category for each value.

>>> cut = s.cut([-1, 1], include_breaks=True).alias("cut")
>>> s.to_frame().with_columns(cut).unnest("cut")
shape: (5, 3)
┌─────┬────────────┬────────────┐
│ foo ┆ breakpoint ┆ category   │
│ --- ┆ ---        ┆ ---        │
│ i64 ┆ f64        ┆ cat        │
╞═════╪════════════╪════════════╡
│ -2  ┆ -1.0       ┆ (-inf, -1] │
│ -1  ┆ -1.0       ┆ (-inf, -1] │
│ 0   ┆ 1.0        ┆ (-1, 1]    │
│ 1   ┆ 1.0        ┆ (-1, 1]    │
│ 2   ┆ inf        ┆ (1, inf]   │
└─────┴────────────┴────────────┘

describe( percentiles: Sequence[float] | float | None = (0.25, 0.5, 0.75), interpolation: RollingInterpolationMethod = 'nearest', ) → DataFrame[source]

Quick summary statistics of a Series.

Series with mixed datatypes will return summary statistics for the datatype of the first value.

Parameters:

percentiles: One or more percentiles to include in the summary statistics (if the Series has a numeric dtype). All values must be in the range [0, 1].
interpolation{‘nearest’, ‘higher’, ‘lower’, ‘midpoint’, ‘linear’}: Interpolation method used when calculating percentiles.

Returns:

DataFrame: Mapping with summary statistics of a Series.

Notes

The median is included by default as the 50% percentile.

Examples

>>> s = pl.Series([1, 2, 3, 4, 5])
>>> s.describe()
shape: (9, 2)
┌────────────┬──────────┐
│ statistic  ┆ value    │
│ ---        ┆ ---      │
│ str        ┆ f64      │
╞════════════╪══════════╡
│ count      ┆ 5.0      │
│ null_count ┆ 0.0      │
│ mean       ┆ 3.0      │
│ std        ┆ 1.581139 │
│ min        ┆ 1.0      │
│ 25%        ┆ 2.0      │
│ 50%        ┆ 3.0      │
│ 75%        ┆ 4.0      │
│ max        ┆ 5.0      │
└────────────┴──────────┘

Non-numeric data types may not have all statistics available.

>>> s = pl.Series(["aa", "aa", None, "bb", "cc"])
>>> s.describe()
shape: (4, 2)
┌────────────┬───────┐
│ statistic  ┆ value │
│ ---        ┆ ---   │
│ str        ┆ str   │
╞════════════╪═══════╡
│ count      ┆ 4     │
│ null_count ┆ 1     │
│ min        ┆ aa    │
│ max        ┆ cc    │
└────────────┴───────┘

diff(n: int = 1, null_behavior: NullBehavior = 'ignore') → Series[source]

Calculate the first discrete difference between shifted items.

Parameters:

n: Number of slots to shift.
null_behavior{‘ignore’, ‘drop’}: How to handle null values.

Examples

>>> s = pl.Series("s", values=[20, 10, 30, 25, 35], dtype=pl.Int8)
>>> s.diff()
shape: (5,)
Series: 's' [i8]
[
    null
    -10
    20
    -5
    10
]

>>> s.diff(n=2)
shape: (5,)
Series: 's' [i8]
[
    null
    null
    10
    15
    5
]

>>> s.diff(n=2, null_behavior="drop")
shape: (3,)
Series: 's' [i8]
[
    10
    15
    5
]

dot(other: Series | ArrayLike) → int | float | None[source]

Compute the dot/inner product between two Series.

Parameters:

other: Series (or array) to compute dot product with.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s2 = pl.Series("b", [4.0, 5.0, 6.0])
>>> s.dot(s2)
32.0

drop_nans() → Series[source]

Drop all floating point NaN values.

The original order of the remaining elements is preserved.

See also

drop_nulls

Notes

A NaN value is not the same as a null value. To drop null values, use drop_nulls().

Examples

>>> s = pl.Series([1.0, None, 3.0, float("nan")])
>>> s.drop_nans()
shape: (3,)
Series: '' [f64]
[
        1.0
        null
        3.0
]

drop_nulls() → Series[source]

Drop all null values.

The original order of the remaining elements is preserved.

See also

drop_nans

Notes

A null value is not the same as a NaN value. To drop NaN values, use drop_nans().

Examples

>>> s = pl.Series([1.0, None, 3.0, float("nan")])
>>> s.drop_nulls()
shape: (3,)
Series: '' [f64]
[
        1.0
        3.0
        NaN
]

property dtype: DataType[source]

Get the data type of this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.dtype
Int64

entropy( base: float = 2.718281828459045, *, normalize: bool = False, ) → float | None[source]

Computes the entropy.

Uses the formula -sum(pk * log(pk) where pk are discrete probabilities.

Parameters:

base: Given base, defaults to e
normalize: Normalize pk if it doesn’t sum to 1.

Examples

>>> a = pl.Series([0.99, 0.005, 0.005])
>>> a.entropy(normalize=True)
0.06293300616044681
>>> b = pl.Series([0.65, 0.10, 0.25])
>>> b.entropy(normalize=True)
0.8568409950394724

eq(other: Any) → Series | Expr[source]: Method equivalent of operator expression series == other.

eq_missing(other: Any) → Series | Expr[source]

Method equivalent of equality operator series == other where None == None.

This differs from the standard ne where null values are propagated.

Parameters:

other: A literal or expression value to compare with.

See also

ne_missing
eq

Examples

>>> s1 = pl.Series("a", [333, 200, None])
>>> s2 = pl.Series("a", [100, 200, None])
>>> s1.eq(s2)
shape: (3,)
Series: 'a' [bool]
[
    false
    true
    null
]
>>> s1.eq_missing(s2)
shape: (3,)
Series: 'a' [bool]
[
    false
    true
    true
]

equals( other: Series, *, check_dtypes: bool = False, check_names: bool = False, null_equal: bool = True, ) → bool[source]

Check whether the Series is equal to another Series.

Parameters:

other: Series to compare with.
check_dtypes: Require data types to match.
check_names: Require names to match.
null_equal: Consider null values as equal.

See also

assert_series_equal

Examples

>>> s1 = pl.Series("a", [1, 2, 3])
>>> s2 = pl.Series("b", [4, 5, 6])
>>> s1.equals(s1)
True
>>> s1.equals(s2)
False

estimated_size(unit: SizeUnit = 'b') → int | float[source]

Return an estimation of the total (heap) allocated size of the Series.

Estimated size is given in the specified unit (bytes by default).

This estimation is the sum of the size of its buffers, validity, including nested arrays. Multiple arrays may share buffers and bitmaps. Therefore, the size of 2 arrays is not the sum of the sizes computed from this function. In particular, [StructArray]’s size is an upper bound.

When an array is sliced, its allocated size remains constant because the buffer unchanged. However, this function will yield a smaller number. This is because this function returns the visible size of the buffer, not its total capacity.

FFI buffers are included in this estimation.

Parameters:

unit{‘b’, ‘kb’, ‘mb’, ‘gb’, ‘tb’}: Scale the returned size to the given unit.

Examples

>>> s = pl.Series("values", list(range(1_000_000)), dtype=pl.UInt32)
>>> s.estimated_size()
4000000
>>> s.estimated_size("mb")
3.814697265625

ewm_mean( *, com: float | None = None, span: float | None = None, half_life: float | None = None, alpha: float | None = None, adjust: bool = True, min_periods: int = 1, ignore_nulls: bool = False, ) → Series[source]

Exponentially-weighted moving average.

Parameters:

com

Specify decay in terms of center of mass, \(\gamma\), with

\[\alpha = \frac{1}{1 + \gamma} \; \forall \; \gamma \geq 0\]

span

Specify decay in terms of span, \(\theta\), with

\[\alpha = \frac{2}{\theta + 1} \; \forall \; \theta \geq 1\]

half_life

Specify decay in terms of half-life, \(\lambda\), with

\[\alpha = 1 - \exp \left\{ \frac{ -\ln(2) }{ \lambda } \right\} \; \forall \; \lambda > 0\]

alpha

Specify smoothing factor alpha directly, \(0 < \alpha \leq 1\).

adjust

Divide by decaying adjustment factor in beginning periods to account for imbalance in relative weightings

When adjust=True (the default) the EW function is calculated using weights \(w_i = (1 - \alpha)^i\)

When adjust=False the EW function is calculated recursively by

\[\begin{split}y_0 &= x_0 \\ y_t &= (1 - \alpha)y_{t - 1} + \alpha x_t\end{split}\]

min_periods

Minimum number of observations in window required to have a value (otherwise result is null).

ignore_nulls

Ignore missing values when calculating weights.

When ignore_nulls=False (default), weights are based on absolute positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \((1-\alpha)^2\) and \(1\) if adjust=True, and \((1-\alpha)^2\) and \(\alpha\) if adjust=False.

When ignore_nulls=True, weights are based on relative positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \(1-\alpha\) and \(1\) if adjust=True, and \(1-\alpha\) and \(\alpha\) if adjust=False.

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.ewm_mean(com=1, ignore_nulls=False)
shape: (3,)
Series: '' [f64]
[
        1.0
        1.666667
        2.428571
]

ewm_mean_by(by: IntoExpr, *, half_life: str | timedelta) → Series[source]

Calculate time-based exponentially weighted moving average.

Given observations \(x_1, x_2, \ldots, x_n\) at times \(t_1, t_2, \ldots, t_n\), the EWMA is calculated as

\[ \begin{align}\begin{aligned}y_0 &= x_0\\\alpha_i &= \exp(-\lambda(t_i - t_{i-1}))\\y_i &= \alpha_i x_i + (1 - \alpha_i) y_{i-1}; \quad i > 0\end{aligned}\end{align} \]

where \(\lambda\) equals \(\ln(2) / \text{half_life}\).

Parameters:

by

Times to calculate average by. Should be DateTime, Date, UInt64, UInt32, Int64, or Int32 data type.

half_life

Unit over which observation decays to half its value.

Can be created either from a timedelta, or by using the following string language:

1ns (1 nanosecond)
1us (1 microsecond)
1ms (1 millisecond)
1s (1 second)
1m (1 minute)
1h (1 hour)
1d (1 day)
1w (1 week)
1i (1 index count)

Or combine them: “3d12h4m25s” # 3 days, 12 hours, 4 minutes, and 25 seconds

Note that half_life is treated as a constant duration - calendar durations such as months (or even days in the time-zone-aware case) are not supported, please express your duration in an approximately equivalent number of hours (e.g. ‘370h’ instead of ‘1mo’).

Returns:

Expr: Float32 if input is Float32, otherwise Float64.

Examples

>>> from datetime import date, timedelta
>>> df = pl.DataFrame(
...     {
...         "values": [0, 1, 2, None, 4],
...         "times": [
...             date(2020, 1, 1),
...             date(2020, 1, 3),
...             date(2020, 1, 10),
...             date(2020, 1, 15),
...             date(2020, 1, 17),
...         ],
...     }
... ).sort("times")
>>> df["values"].ewm_mean_by(df["times"], half_life="4d")
shape: (5,)
Series: 'values' [f64]
[
        0.0
        0.292893
        1.492474
        null
        3.254508
]

ewm_std( *, com: float | None = None, span: float | None = None, half_life: float | None = None, alpha: float | None = None, adjust: bool = True, bias: bool = False, min_periods: int = 1, ignore_nulls: bool = False, ) → Series[source]

Exponentially-weighted moving standard deviation.

Parameters:

com

Specify decay in terms of center of mass, \(\gamma\), with

\[\alpha = \frac{1}{1 + \gamma} \; \forall \; \gamma \geq 0\]

span

Specify decay in terms of span, \(\theta\), with

\[\alpha = \frac{2}{\theta + 1} \; \forall \; \theta \geq 1\]

half_life

Specify decay in terms of half-life, \(\lambda\), with

\[\alpha = 1 - \exp \left\{ \frac{ -\ln(2) }{ \lambda } \right\} \; \forall \; \lambda > 0\]

alpha

Specify smoothing factor alpha directly, \(0 < \alpha \leq 1\).

adjust

Divide by decaying adjustment factor in beginning periods to account for imbalance in relative weightings

When adjust=True (the default) the EW function is calculated using weights \(w_i = (1 - \alpha)^i\)

When adjust=False the EW function is calculated recursively by

\[\begin{split}y_0 &= x_0 \\ y_t &= (1 - \alpha)y_{t - 1} + \alpha x_t\end{split}\]

bias

When bias=False, apply a correction to make the estimate statistically unbiased.

min_periods

Minimum number of observations in window required to have a value (otherwise result is null).

ignore_nulls

Ignore missing values when calculating weights.

When ignore_nulls=False (default), weights are based on absolute positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \((1-\alpha)^2\) and \(1\) if adjust=True, and \((1-\alpha)^2\) and \(\alpha\) if adjust=False.

When ignore_nulls=True, weights are based on relative positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \(1-\alpha\) and \(1\) if adjust=True, and \(1-\alpha\) and \(\alpha\) if adjust=False.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.ewm_std(com=1, ignore_nulls=False)
shape: (3,)
Series: 'a' [f64]
[
    0.0
    0.707107
    0.963624
]

ewm_var( *, com: float | None = None, span: float | None = None, half_life: float | None = None, alpha: float | None = None, adjust: bool = True, bias: bool = False, min_periods: int = 1, ignore_nulls: bool = False, ) → Series[source]

Exponentially-weighted moving variance.

Parameters:

com

Specify decay in terms of center of mass, \(\gamma\), with

\[\alpha = \frac{1}{1 + \gamma} \; \forall \; \gamma \geq 0\]

span

Specify decay in terms of span, \(\theta\), with

\[\alpha = \frac{2}{\theta + 1} \; \forall \; \theta \geq 1\]

half_life

Specify decay in terms of half-life, \(\lambda\), with

\[\alpha = 1 - \exp \left\{ \frac{ -\ln(2) }{ \lambda } \right\} \; \forall \; \lambda > 0\]

alpha

Specify smoothing factor alpha directly, \(0 < \alpha \leq 1\).

adjust

Divide by decaying adjustment factor in beginning periods to account for imbalance in relative weightings

When adjust=True (the default) the EW function is calculated using weights \(w_i = (1 - \alpha)^i\)

When adjust=False the EW function is calculated recursively by

\[\begin{split}y_0 &= x_0 \\ y_t &= (1 - \alpha)y_{t - 1} + \alpha x_t\end{split}\]

bias

When bias=False, apply a correction to make the estimate statistically unbiased.

min_periods

Minimum number of observations in window required to have a value (otherwise result is null).

ignore_nulls

Ignore missing values when calculating weights.

When ignore_nulls=False (default), weights are based on absolute positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \((1-\alpha)^2\) and \(1\) if adjust=True, and \((1-\alpha)^2\) and \(\alpha\) if adjust=False.

When ignore_nulls=True, weights are based on relative positions. For example, the weights of \(x_0\) and \(x_2\) used in calculating the final weighted average of [\(x_0\), None, \(x_2\)] are \(1-\alpha\) and \(1\) if adjust=True, and \(1-\alpha\) and \(\alpha\) if adjust=False.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.ewm_var(com=1, ignore_nulls=False)
shape: (3,)
Series: 'a' [f64]
[
    0.0
    0.5
    0.928571
]

exp() → Series[source]

Compute the exponential, element-wise.

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.exp()
shape: (3,)
Series: '' [f64]
[
    2.718282
    7.389056
    20.085537
]

explode() → Series[source]

Explode a list Series.

This means that every item is expanded to a new row.

Returns:

Series: Series with the data type of the list elements.

See also

Series.list.explode: Explode a list column.

Examples

>>> s = pl.Series("a", [[1, 2, 3], [4, 5, 6]])
>>> s
shape: (2,)
Series: 'a' [list[i64]]
[
        [1, 2, 3]
        [4, 5, 6]
]
>>> s.explode()
shape: (6,)
Series: 'a' [i64]
[
        1
        2
        3
        4
        5
        6
]

extend(other: Series) → Self[source]

Extend the memory backed by this Series with the values from another.

Different from append, which adds the chunks from other to the chunks of this series, extend appends the data from other to the underlying memory locations and thus may cause a reallocation (which is expensive).

If this does not cause a reallocation, the resulting data structure will not have any extra chunks and thus will yield faster queries.

Prefer extend over append when you want to do a query after a single append. For instance, during online operations where you add n rows and rerun a query.

Prefer append over extend when you want to append many times before doing a query. For instance, when you read in multiple files and want to store them in a single Series. In the latter case, finish the sequence of append operations with a rechunk.

Parameters:

other: Series to extend the series with.

Warning

This method modifies the series in-place. The series is returned for convenience only.

See also

append

Examples

>>> a = pl.Series("a", [1, 2, 3])
>>> b = pl.Series("b", [4, 5])
>>> a.extend(b)
shape: (5,)
Series: 'a' [i64]
[
    1
    2
    3
    4
    5
]

The resulting series will consist of a single chunk.

>>> a.n_chunks()
1

extend_constant(value: IntoExpr, n: int | IntoExprColumn) → Series[source]

Extremely fast method for extending the Series with ‘n’ copies of a value.

Parameters:

value: A constant literal value or a unit expressioin with which to extend the expression result Series; can pass None to extend with nulls.
n: The number of additional values that will be added.

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.extend_constant(99, n=2)
shape: (5,)
Series: '' [i64]
[
        1
        2
        3
        99
        99
]

fill_nan(value: int | float | Expr | None) → Series[source]

Fill floating point NaN value with a fill value.

Parameters:

value: Value used to fill NaN values.

Warning

Note that floating point NaNs (Not a Number) are not missing values. To replace missing values, use fill_null().

See also

fill_null

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, float("nan")])
>>> s.fill_nan(0)
shape: (4,)
Series: 'a' [f64]
[
        1.0
        2.0
        3.0
        0.0
]

fill_null( value: Any | Expr | None = None, strategy: FillNullStrategy | None = None, limit: int | None = None, ) → Series[source]

Fill null values using the specified value or strategy.

Parameters:

value: Value used to fill null values.
strategy{None, ‘forward’, ‘backward’, ‘min’, ‘max’, ‘mean’, ‘zero’, ‘one’}: Strategy used to fill null values.
limit: Number of consecutive null values to fill when using the ‘forward’ or ‘backward’ strategy.

See also

fill_nan

Examples

>>> s = pl.Series("a", [1, 2, 3, None])
>>> s.fill_null(strategy="forward")
shape: (4,)
Series: 'a' [i64]
[
    1
    2
    3
    3
]
>>> s.fill_null(strategy="min")
shape: (4,)
Series: 'a' [i64]
[
    1
    2
    3
    1
]
>>> s = pl.Series("b", ["x", None, "z"])
>>> s.fill_null(pl.lit(""))
shape: (3,)
Series: 'b' [str]
[
    "x"
    ""
    "z"
]

filter(predicate: Series | list[bool]) → Self[source]

Filter elements by a boolean mask.

The original order of the remaining elements is preserved.

Elements where the filter does not evaluate to True are discarded, including nulls.

Parameters:

predicate: Boolean mask.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> mask = pl.Series("", [True, False, True])
>>> s.filter(mask)
shape: (2,)
Series: 'a' [i64]
[
        1
        3
]

property flags: dict[str, bool][source]

Get flags that are set on the Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.flags
{'SORTED_ASC': False, 'SORTED_DESC': False}

floor() → Series[source]

Rounds down to the nearest integer value.

Only works on floating point Series.

Examples

>>> s = pl.Series("a", [1.12345, 2.56789, 3.901234])
>>> s.floor()
shape: (3,)
Series: 'a' [f64]
[
        1.0
        2.0
        3.0
]

gather(indices: int | list[int] | Expr | Series | np.ndarray[Any, Any]) → Series[source]

Take values by index.

Parameters:

indices: Index location used for selection.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4])
>>> s.gather([1, 3])
shape: (2,)
Series: 'a' [i64]
[
        2
        4
]

gather_every(n: int, offset: int = 0) → Series[source]

Take every nth value in the Series and return as new Series.

Parameters:

n: Gather every n-th row.
offset: Start the row index at this offset.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4])
>>> s.gather_every(2)
shape: (2,)
Series: 'a' [i64]
[
    1
    3
]
>>> s.gather_every(2, offset=1)
shape: (2,)
Series: 'a' [i64]
[
    2
    4
]

ge(other: Any) → Series | Expr[source]: Method equivalent of operator expression series >= other.

get_chunks() → list[Series][source]

Get the chunks of this Series as a list of Series.

Examples

>>> s1 = pl.Series("a", [1, 2, 3])
>>> s2 = pl.Series("a", [4, 5, 6])
>>> s = pl.concat([s1, s2], rechunk=False)
>>> s.get_chunks()
[shape: (3,)
Series: 'a' [i64]
[
        1
        2
        3
], shape: (3,)
Series: 'a' [i64]
[
        4
        5
        6
]]

gt(other: Any) → Series | Expr[source]: Method equivalent of operator expression series > other.

has_nulls() → bool[source]

Check whether the Series contains one or more null values.

Examples

>>> s = pl.Series([1, 2, None])
>>> s.has_nulls()
True
>>> s[:2].has_nulls()
False

has_validity() → bool[source]: Check whether the Series contains one or more null values.

Deprecated since version 0.20.30: Use has_nulls() instead.

hash( seed: int = 0, seed_1: int | None = None, seed_2: int | None = None, seed_3: int | None = None, ) → Series[source]

Hash the Series.

The hash value is of type UInt64.

Parameters:

seed: Random seed parameter. Defaults to 0.
seed_1: Random seed parameter. Defaults to seed if not set.
seed_2: Random seed parameter. Defaults to seed if not set.
seed_3: Random seed parameter. Defaults to seed if not set.

Notes

This implementation of hash does not guarantee stable results across different Polars versions. Its stability is only guaranteed within a single version.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.hash(seed=42)  
shape: (3,)
Series: 'a' [u64]
[
    10734580197236529959
    3022416320763508302
    13756996518000038261
]

head(n: int = 10) → Series[source]

Get the first n elements.

Parameters:

n: Number of elements to return. If a negative value is passed, return all elements except the last abs(n).

See also

tail, slice

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.head(3)
shape: (3,)
Series: 'a' [i64]
[
        1
        2
        3
]

Pass a negative value to get all rows except the last abs(n).

>>> s.head(-3)
shape: (2,)
Series: 'a' [i64]
[
        1
        2
]

hist( bins: list[float] | None = None, *, bin_count: int | None = None, include_category: bool = True, include_breakpoint: bool = True, ) → DataFrame[source]

Bin values into buckets and count their occurrences.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

bins: Discretizations to make. If None given, we determine the boundaries based on the data.
bin_count: If no bins provided, this will be used to determine the distance of the bins
include_breakpoint: Include a column that indicates the upper breakpoint.
include_category: Include a column that shows the intervals as categories.

Returns:

DataFrame

Examples

>>> a = pl.Series("a", [1, 3, 8, 8, 2, 1, 3])
>>> a.hist(bin_count=4)
shape: (5, 3)
┌────────────┬─────────────┬───────┐
│ breakpoint ┆ category    ┆ count │
│ ---        ┆ ---         ┆ ---   │
│ f64        ┆ cat         ┆ u32   │
╞════════════╪═════════════╪═══════╡
│ 0.0        ┆ (-inf, 0.0] ┆ 0     │
│ 2.25       ┆ (0.0, 2.25] ┆ 3     │
│ 4.5        ┆ (2.25, 4.5] ┆ 2     │
│ 6.75       ┆ (4.5, 6.75] ┆ 0     │
│ inf        ┆ (6.75, inf] ┆ 2     │
└────────────┴─────────────┴───────┘

implode() → Self[source]

Aggregate values into a list.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.implode()
shape: (1,)
Series: 'a' [list[i64]]
[
    [1, 2, 3]
]

interpolate(method: InterpolationMethod = 'linear') → Series[source]

Fill null values using interpolation.

Parameters:

method{‘linear’, ‘nearest’}: Interpolation method.

Examples

>>> s = pl.Series("a", [1, 2, None, None, 5])
>>> s.interpolate()
shape: (5,)
Series: 'a' [f64]
[
    1.0
    2.0
    3.0
    4.0
    5.0
]

interpolate_by(by: IntoExpr) → Series[source]

Fill null values using interpolation based on another column.

Parameters:

by: Column to interpolate values based on.

Examples

Fill null values using linear interpolation.

>>> s = pl.Series([1, None, None, 3])
>>> by = pl.Series([1, 2, 7, 8])
>>> s.interpolate_by(by)
shape: (4,)
Series: '' [f64]
[
    1.0
    1.285714
    2.714286
    3.0
]

is_between( lower_bound: IntoExpr, upper_bound: IntoExpr, closed: ClosedInterval = 'both', ) → Series[source]

Get a boolean mask of the values that are between the given lower/upper bounds.

Parameters:

lower_bound: Lower bound value. Accepts expression input. Non-expression inputs (including strings) are parsed as literals.
upper_bound: Upper bound value. Accepts expression input. Non-expression inputs (including strings) are parsed as literals.
closed{‘both’, ‘left’, ‘right’, ‘none’}: Define which sides of the interval are closed (inclusive).

Notes

If the value of the lower_bound is greater than that of the upper_bound then the result will be False, as no value can satisfy the condition.

Examples

>>> s = pl.Series("num", [1, 2, 3, 4, 5])
>>> s.is_between(2, 4)
shape: (5,)
Series: 'num' [bool]
[
    false
    true
    true
    true
    false
]

Use the closed argument to include or exclude the values at the bounds:

>>> s.is_between(2, 4, closed="left")
shape: (5,)
Series: 'num' [bool]
[
    false
    true
    true
    false
    false
]

You can also use strings as well as numeric/temporal values:

>>> s = pl.Series("s", ["a", "b", "c", "d", "e"])
>>> s.is_between("b", "d", closed="both")
shape: (5,)
Series: 's' [bool]
[
    false
    true
    true
    true
    false
]

is_duplicated() → Series[source]

Get mask of all duplicated values.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.is_duplicated()
shape: (4,)
Series: 'a' [bool]
[
        false
        true
        true
        false
]

is_empty() → bool[source]

Check if the Series is empty.

Examples

>>> s = pl.Series("a", [], dtype=pl.Float32)
>>> s.is_empty()
True

is_finite() → Series[source]

Returns a boolean Series indicating which values are finite.

Returns:

Series: Series of data type Boolean.

Examples

>>> import numpy as np
>>> s = pl.Series("a", [1.0, 2.0, np.inf])
>>> s.is_finite()
shape: (3,)
Series: 'a' [bool]
[
        true
        true
        false
]

is_first_distinct() → Series[source]

Return a boolean mask indicating the first occurrence of each distinct value.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series([1, 1, 2, 3, 2])
>>> s.is_first_distinct()
shape: (5,)
Series: '' [bool]
[
        true
        false
        true
        true
        false
]

is_in( other: Series | Collection[Any], ) → Series[source]

Check if elements of this Series are in the other Series.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s2 = pl.Series("b", [2, 4])
>>> s2.is_in(s)
shape: (2,)
Series: 'b' [bool]
[
        true
        false
]

>>> # check if some values are a member of sublists
>>> sets = pl.Series("sets", [[1, 2, 3], [1, 2], [9, 10]])
>>> optional_members = pl.Series("optional_members", [1, 2, 3])
>>> print(sets)
shape: (3,)
Series: 'sets' [list[i64]]
[
    [1, 2, 3]
    [1, 2]
    [9, 10]
]
>>> print(optional_members)
shape: (3,)
Series: 'optional_members' [i64]
[
    1
    2
    3
]
>>> optional_members.is_in(sets)
shape: (3,)
Series: 'optional_members' [bool]
[
    true
    true
    false
]

is_infinite() → Series[source]

Returns a boolean Series indicating which values are infinite.

Returns:

Series: Series of data type Boolean.

Examples

>>> import numpy as np
>>> s = pl.Series("a", [1.0, 2.0, np.inf])
>>> s.is_infinite()
shape: (3,)
Series: 'a' [bool]
[
        false
        false
        true
]

is_last_distinct() → Series[source]

Return a boolean mask indicating the last occurrence of each distinct value.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series([1, 1, 2, 3, 2])
>>> s.is_last_distinct()
shape: (5,)
Series: '' [bool]
[
        false
        true
        false
        true
        true
]

is_nan() → Series[source]

Returns a boolean Series indicating which values are not NaN.

Returns:

Series: Series of data type Boolean.

Examples

>>> import numpy as np
>>> s = pl.Series("a", [1.0, 2.0, 3.0, np.nan])
>>> s.is_nan()
shape: (4,)
Series: 'a' [bool]
[
        false
        false
        false
        true
]

is_not_nan() → Series[source]

Returns a boolean Series indicating which values are not NaN.

Returns:

Series: Series of data type Boolean.

Examples

>>> import numpy as np
>>> s = pl.Series("a", [1.0, 2.0, 3.0, np.nan])
>>> s.is_not_nan()
shape: (4,)
Series: 'a' [bool]
[
        true
        true
        true
        false
]

is_not_null() → Series[source]

Returns a boolean Series indicating which values are not null.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, None])
>>> s.is_not_null()
shape: (4,)
Series: 'a' [bool]
[
    true
    true
    true
    false
]

is_null() → Series[source]

Returns a boolean Series indicating which values are null.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, None])
>>> s.is_null()
shape: (4,)
Series: 'a' [bool]
[
    false
    false
    false
    true
]

is_sorted(*, descending: bool = False, nulls_last: bool = False) → bool[source]

Check if the Series is sorted.

Parameters:

descending: Check if the Series is sorted in descending order
nulls_last: Set nulls at the end of the Series in sorted check.

Examples

>>> s = pl.Series([1, 3, 2])
>>> s.is_sorted()
False

>>> s = pl.Series([3, 2, 1])
>>> s.is_sorted(descending=True)
True

is_unique() → Series[source]

Get mask of all unique values.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.is_unique()
shape: (4,)
Series: 'a' [bool]
[
        true
        false
        false
        true
]

item(index: int | None = None) → Any[source]

Return the Series as a scalar, or return the element at the given index.

If no index is provided, this is equivalent to s[0], with a check that the shape is (1,). With an index, this is equivalent to s[index].

Examples

>>> s1 = pl.Series("a", [1])
>>> s1.item()
1
>>> s2 = pl.Series("a", [9, 8, 7])
>>> s2.cum_sum().item(-1)
24

kurtosis(*, fisher: bool = True, bias: bool = True) → float | None[source]

Compute the kurtosis (Fisher or Pearson) of a dataset.

Kurtosis is the fourth central moment divided by the square of the variance. If Fisher’s definition is used, then 3.0 is subtracted from the result to give 0.0 for a normal distribution. If bias is False then the kurtosis is calculated using k statistics to eliminate bias coming from biased moment estimators

See scipy.stats for more information

Parameters:

fisherbool, optional: If True, Fisher’s definition is used (normal ==> 0.0). If False, Pearson’s definition is used (normal ==> 3.0).
biasbool, optional: If False, the calculations are corrected for statistical bias.

Examples

>>> s = pl.Series("grades", [66, 79, 54, 97, 96, 70, 69, 85, 93, 75])
>>> s.kurtosis()
-1.0522623626787952
>>> s.kurtosis(fisher=False)
1.9477376373212048
>>> s.kurtosis(fisher=False, bias=False)
2.1040361802642726

le(other: Any) → Series | Expr[source]: Method equivalent of operator expression series <= other.

len() → int[source]

Return the number of elements in the Series.

Null values count towards the total.

See also

count

Examples

>>> s = pl.Series("a", [1, 2, None])
>>> s.len()
3

limit(n: int = 10) → Series[source]

Get the first n elements.

Alias for Series.head().

Parameters:

n: Number of elements to return. If a negative value is passed, return all elements except the last abs(n).

See also

head

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.limit(3)
shape: (3,)
Series: 'a' [i64]
[
    1
    2
    3
]

Pass a negative value to get all rows except the last abs(n).

>>> s.limit(-3)
shape: (2,)
Series: 'a' [i64]
[
        1
        2
]

log(base: float = 2.718281828459045) → Series[source]

Compute the logarithm to a given base.

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.log()
shape: (3,)
Series: '' [f64]
[
    0.0
    0.693147
    1.098612
]

log10() → Series[source]

Compute the base 10 logarithm of the input array, element-wise.

Examples

>>> s = pl.Series([10, 100, 1000])
>>> s.log10()
shape: (3,)
Series: '' [f64]
[
    1.0
    2.0
    3.0
]

log1p() → Series[source]

Compute the natural logarithm of the input array plus one, element-wise.

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.log1p()
shape: (3,)
Series: '' [f64]
[
    0.693147
    1.098612
    1.386294
]

lower_bound() → Self[source]

Return the lower bound of this Series’ dtype as a unit Series.

See also

upper_bound: return the upper bound of the given Series’ dtype.

Examples

>>> s = pl.Series("s", [-1, 0, 1], dtype=pl.Int32)
>>> s.lower_bound()
shape: (1,)
Series: 's' [i32]
[
    -2147483648
]

>>> s = pl.Series("s", [1.0, 2.5, 3.0], dtype=pl.Float32)
>>> s.lower_bound()
shape: (1,)
Series: 's' [f32]
[
    -inf
]

lt(other: Any) → Series | Expr[source]: Method equivalent of operator expression series < other.

map_elements( function: Callable[[Any], Any], return_dtype: PolarsDataType | None = None, *, skip_nulls: bool = True, ) → Self[source]

Map a custom/user-defined function (UDF) over elements in this Series.

Warning

This method is much slower than the native expressions API. Only use it if you cannot implement your logic otherwise.

Suppose that the function is: x ↦ sqrt(x):

For mapping elements of a series, consider: s.sqrt().
For mapping inner elements of lists, consider: s.list.eval(pl.element().sqrt()).
For mapping elements of struct fields, consider: s.struct.field("field_name").sqrt().

If the function returns a different datatype, the return_dtype arg should be set, otherwise the method will fail.

Implementing logic using a Python function is almost always significantly slower and more memory intensive than implementing the same logic using the native expression API because:

The native expression engine runs in Rust; UDFs run in Python.
Use of Python UDFs forces the DataFrame to be materialized in memory.
Polars-native expressions can be parallelised (UDFs typically cannot).
Polars-native expressions can be logically optimised (UDFs cannot).

Wherever possible you should strongly prefer the native expression API to achieve the best performance.

Parameters:

function: Custom function or lambda.
return_dtype: Output datatype. If not set, the dtype will be inferred based on the first non-null value that is returned by the function.
skip_nulls: Nulls will be skipped and not passed to the python function. This is faster because python can be skipped and because we call more specialized functions.

Returns:

Series

Warning

If return_dtype is not provided, this may lead to unexpected results. We allow this, but it is considered a bug in the user’s query.

Notes

If your function is expensive and you don’t want it to be called more than once for a given input, consider applying an @lru_cache decorator to it. If your data is suitable you may achieve significant speedups.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.map_elements(lambda x: x + 10, return_dtype=pl.Int64)  
shape: (3,)
Series: 'a' [i64]
[
        11
        12
        13
]

max() → PythonLiteral | None[source]

Get the maximum value in this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.max()
3

mean() → PythonLiteral | None[source]

Reduce this Series to the mean value.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.mean()
2.0

median() → PythonLiteral | None[source]

Get the median of this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.median()
2.0

min() → PythonLiteral | None[source]

Get the minimal value in this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.min()
1

mode() → Series[source]

Compute the most occurring value(s).

Can return multiple Values.

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.mode()
shape: (1,)
Series: 'a' [i64]
[
        2
]

n_chunks() → int[source]

Get the number of chunks that this Series contains.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.n_chunks()
1
>>> s2 = pl.Series("a", [4, 5, 6])

Concatenate Series with rechunk = True

>>> pl.concat([s, s2], rechunk=True).n_chunks()
1

Concatenate Series with rechunk = False

>>> pl.concat([s, s2], rechunk=False).n_chunks()
2

n_unique() → int[source]

Count the number of unique values in this Series.

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.n_unique()
3

property name: str[source]

Get the name of this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.name
'a'

Get maximum value, but propagate/poison encountered NaN values.

This differs from numpy’s nanmax as numpy defaults to propagating NaN values, whereas polars defaults to ignoring them.

Examples

>>> s = pl.Series("a", [1, 3, 4])
>>> s.nan_max()
4

>>> s = pl.Series("a", [1.0, float("nan"), 4.0])
>>> s.nan_max()
nan

Get minimum value, but propagate/poison encountered NaN values.

This differs from numpy’s nanmax as numpy defaults to propagating NaN values, whereas polars defaults to ignoring them.

Examples

>>> s = pl.Series("a", [1, 3, 4])
>>> s.nan_min()
1

>>> s = pl.Series("a", [1.0, float("nan"), 4.0])
>>> s.nan_min()
nan

ne(other: Any) → Series | Expr[source]: Method equivalent of operator expression series != other.

ne_missing(other: Any) → Series | Expr[source]

Method equivalent of equality operator series != other where None == None.

This differs from the standard ne where null values are propagated.

Parameters:

other: A literal or expression value to compare with.

See also

eq_missing
ne

Examples

>>> s1 = pl.Series("a", [333, 200, None])
>>> s2 = pl.Series("a", [100, 200, None])
>>> s1.ne(s2)
shape: (3,)
Series: 'a' [bool]
[
    true
    false
    null
]
>>> s1.ne_missing(s2)
shape: (3,)
Series: 'a' [bool]
[
    true
    false
    false
]

new_from_index(index: int, length: int) → Self[source]

Create a new Series filled with values from the given index.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.new_from_index(1, 3)
shape: (3,)
Series: 'a' [i64]
[
    2
    2
    2
]

not_() → Series[source]

Negate a boolean Series.

Returns:

Series: Series of data type Boolean.

Examples

>>> s = pl.Series("a", [True, False, False])
>>> s.not_()
shape: (3,)
Series: 'a' [bool]
[
    false
    true
    true
]

null_count() → int[source]

Count the null values in this Series.

Examples

>>> s = pl.Series([1, None, None])
>>> s.null_count()
2

pct_change(n: int | IntoExprColumn = 1) → Series[source]

Computes percentage change between values.

Percentage change (as fraction) between current element and most-recent non-null element at least n period(s) before the current element.

Computes the change from the previous row by default.

Parameters:

n: periods to shift for forming percent change.

Examples

>>> pl.Series(range(10)).pct_change()
shape: (10,)
Series: '' [f64]
[
    null
    inf
    1.0
    0.5
    0.333333
    0.25
    0.2
    0.166667
    0.142857
    0.125
]

>>> pl.Series([1, 2, 4, 8, 16, 32, 64, 128, 256, 512]).pct_change(2)
shape: (10,)
Series: '' [f64]
[
    null
    null
    3.0
    3.0
    3.0
    3.0
    3.0
    3.0
    3.0
    3.0
]

peak_max() → Self[source]

Get a boolean mask of the local maximum peaks.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.peak_max()
shape: (5,)
Series: 'a' [bool]
[
        false
        false
        false
        false
        true
]

peak_min() → Self[source]

Get a boolean mask of the local minimum peaks.

Examples

>>> s = pl.Series("a", [4, 1, 3, 2, 5])
>>> s.peak_min()
shape: (5,)
Series: 'a' [bool]
[
    false
    true
    false
    true
    false
]

property plot: hvPlotTabularPolars[source]

Create a plot namespace.

Warning

This functionality is currently considered unstable. It may be changed at any point without it being considered a breaking change.

Polars does not implement plotting logic itself, but instead defers to hvplot. Please see the hvplot reference gallery for more information and documentation.

Examples

Histogram:

>>> s = pl.Series("values", [1, 4, 2])
>>> s.plot.hist()  

KDE plot (note: in addition to hvplot, this one also requires scipy):

>>> s.plot.kde()  

For more info on what you can pass, you can use hvplot.help:

>>> import hvplot  
>>> hvplot.help("hist")  

pow( exponent: int | float | Series, ) → Series[source]

Raise to the power of the given exponent.

If the exponent is float, the result follows the dtype of exponent. Otherwise, it follows dtype of base.

Parameters:

exponent: The exponent. Accepts Series input.

Examples

Raising integers to positive integers results in integers:

>>> s = pl.Series("foo", [1, 2, 3, 4])
>>> s.pow(3)
shape: (4,)
Series: 'foo' [i64]
[
    1
    8
    27
    64
]

In order to raise integers to negative integers, you can cast either the base or the exponent to float:

>>> s.pow(-3.0)
shape: (4,)
Series: 'foo' [f64]
[
        1.0
        0.125
        0.037037
        0.015625
]

product() → int | float[source]

Reduce this Series to the product value.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.product()
6

qcut( quantiles: Sequence[float] | int, *, labels: Sequence[str] | None = None, left_closed: bool = False, allow_duplicates: bool = False, include_breaks: bool = False, ) → Series[source]

Bin continuous values into discrete categories based on their quantiles.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

quantiles: Either a list of quantile probabilities between 0 and 1 or a positive integer determining the number of bins with uniform probability.
labels: Names of the categories. The number of labels must be equal to the number of cut points plus one.
left_closed: Set the intervals to be left-closed instead of right-closed.
allow_duplicates: If set to True, duplicates in the resulting quantiles are dropped, rather than raising a DuplicateError. This can happen even with unique probabilities, depending on the data.
include_breaks: Include a column with the right endpoint of the bin each observation falls in. This will change the data type of the output from a Categorical to a Struct.

Returns:

Series: Series of data type Categorical if include_breaks is set to False (default), otherwise a Series of data type Struct.

See also

cut

Examples

Divide a column into three categories according to pre-defined quantile probabilities.

>>> s = pl.Series("foo", [-2, -1, 0, 1, 2])
>>> s.qcut([0.25, 0.75], labels=["a", "b", "c"])
shape: (5,)
Series: 'foo' [cat]
[
        "a"
        "a"
        "b"
        "b"
        "c"
]

Divide a column into two categories using uniform quantile probabilities.

>>> s.qcut(2, labels=["low", "high"], left_closed=True)
shape: (5,)
Series: 'foo' [cat]
[
        "low"
        "low"
        "high"
        "high"
        "high"
]

Create a DataFrame with the breakpoint and category for each value.

>>> cut = s.qcut([0.25, 0.75], include_breaks=True).alias("cut")
>>> s.to_frame().with_columns(cut).unnest("cut")
shape: (5, 3)
┌─────┬────────────┬────────────┐
│ foo ┆ breakpoint ┆ category   │
│ --- ┆ ---        ┆ ---        │
│ i64 ┆ f64        ┆ cat        │
╞═════╪════════════╪════════════╡
│ -2  ┆ -1.0       ┆ (-inf, -1] │
│ -1  ┆ -1.0       ┆ (-inf, -1] │
│ 0   ┆ 1.0        ┆ (-1, 1]    │
│ 1   ┆ 1.0        ┆ (-1, 1]    │
│ 2   ┆ inf        ┆ (1, inf]   │
└─────┴────────────┴────────────┘

quantile( quantile: float, interpolation: RollingInterpolationMethod = 'nearest', ) → float | None[source]

Get the quantile value of this Series.

Parameters:

quantile: Quantile between 0.0 and 1.0.
interpolation{‘nearest’, ‘higher’, ‘lower’, ‘midpoint’, ‘linear’}: Interpolation method.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.quantile(0.5)
2.0

rank( method: RankMethod = 'average', *, descending: bool = False, seed: int | None = None, ) → Series[source]

Assign ranks to data, dealing with ties appropriately.

Parameters:

method{‘average’, ‘min’, ‘max’, ‘dense’, ‘ordinal’, ‘random’}

The method used to assign ranks to tied elements. The following methods are available (default is ‘average’):

‘average’ : The average of the ranks that would have been assigned to all the tied values is assigned to each value.
‘min’ : The minimum of the ranks that would have been assigned to all the tied values is assigned to each value. (This is also referred to as “competition” ranking.)
‘max’ : The maximum of the ranks that would have been assigned to all the tied values is assigned to each value.
‘dense’ : Like ‘min’, but the rank of the next highest element is assigned the rank immediately after those assigned to the tied elements.
‘ordinal’ : All values are given a distinct rank, corresponding to the order that the values occur in the Series.
‘random’ : Like ‘ordinal’, but the rank for ties is not dependent on the order that the values occur in the Series.

descending

Rank in descending order.

seed

If method="random", use this as seed.

Examples

The ‘average’ method:

>>> s = pl.Series("a", [3, 6, 1, 1, 6])
>>> s.rank()
shape: (5,)
Series: 'a' [f64]
[
    3.0
    4.5
    1.5
    1.5
    4.5
]

The ‘ordinal’ method:

>>> s = pl.Series("a", [3, 6, 1, 1, 6])
>>> s.rank("ordinal")
shape: (5,)
Series: 'a' [u32]
[
    3
    4
    1
    2
    5
]

rechunk(*, in_place: bool = False) → Self[source]

Create a single chunk of memory for this Series.

Parameters:

in_place: In place or not.

Examples

>>> s1 = pl.Series("a", [1, 2, 3])
>>> s1.n_chunks()
1
>>> s2 = pl.Series("a", [4, 5, 6])
>>> s = pl.concat([s1, s2], rechunk=False)
>>> s.n_chunks()
2
>>> s.rechunk(in_place=True)
shape: (6,)
Series: 'a' [i64]
[
        1
        2
        3
        4
        5
        6
]
>>> s.n_chunks()
1

reinterpret(*, signed: bool = True) → Series[source]

Reinterpret the underlying bits as a signed/unsigned integer.

This operation is only allowed for 64bit integers. For lower bits integers, you can safely use that cast operation.

Parameters:

signed: If True, reinterpret as pl.Int64. Otherwise, reinterpret as pl.UInt64.

Examples

>>> s = pl.Series("a", [-(2**60), -2, 3])
>>> s
shape: (3,)
Series: 'a' [i64]
[
        -1152921504606846976
        -2
        3
]
>>> s.reinterpret(signed=False)
shape: (3,)
Series: 'a' [u64]
[
        17293822569102704640
        18446744073709551614
        3
]

rename(name: str) → Series[source]

Rename this Series.

Alias for Series.alias().

Parameters:

name: New name.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.rename("b")
shape: (3,)
Series: 'b' [i64]
[
        1
        2
        3
]

Replace values by different values of the same data type.

Parameters:

old: Value or sequence of values to replace. Also accepts a mapping of values to their replacement as syntactic sugar for replace(old=Series(mapping.keys()), new=Series(mapping.values())).
new: Value or sequence of values to replace by. Length must match the length of old or have length 1.
default: Set values that were not replaced to this value. Defaults to keeping the original value. Accepts expression input. Non-expression inputs are parsed as literals.

Deprecated since version 0.20.31: Use replace_all() instead to set a default while replacing values.
return_dtype: The data type of the resulting expression. If set to None (default), the data type is determined automatically based on the other inputs.

Deprecated since version 0.20.31: Use replace_all() instead to set a return data type while replacing values.

See also

replace_strict
str.replace

Notes

The global string cache must be enabled when replacing categorical values.

Examples

Replace a single value by another value. Values that were not replaced remain unchanged.

>>> s = pl.Series([1, 2, 2, 3])
>>> s.replace(2, 100)
shape: (4,)
Series: '' [i64]
[
        1
        100
        100
        3
]

Replace multiple values by passing sequences to the old and new parameters.

>>> s.replace([2, 3], [100, 200])
shape: (4,)
Series: '' [i64]
[
        1
        100
        100
        200
]

Passing a mapping with replacements is also supported as syntactic sugar.

>>> mapping = {2: 100, 3: 200}
>>> s.replace(mapping)
shape: (4,)
Series: '' [i64]
[
        1
        100
        100
        200
]

The original data type is preserved when replacing by values of a different data type. Use replace_strict() to replace and change the return data type.

>>> s = pl.Series(["x", "y", "z"])
>>> mapping = {"x": 1, "y": 2, "z": 3}
>>> s.replace(mapping)
shape: (3,)
Series: '' [str]
[
        "1"
        "2"
        "3"
]

Replace all values by different values.

Parameters:

old: Value or sequence of values to replace. Also accepts a mapping of values to their replacement as syntactic sugar for replace_all(old=Series(mapping.keys()), new=Series(mapping.values())).
new: Value or sequence of values to replace by. Length must match the length of old or have length 1.
default: Set values that were not replaced to this value. If no default is specified, (default), an error is raised if any values were not replaced. Accepts expression input. Non-expression inputs are parsed as literals.
return_dtype: The data type of the resulting Series. If set to None (default), the data type is determined automatically based on the other inputs.

Raises:

InvalidOperationError: If any non-null values in the original column were not replaced, and no default was specified.

See also

replace
str.replace

Notes

The global string cache must be enabled when replacing categorical values.

Examples

Replace values by passing sequences to the old and new parameters.

>>> s = pl.Series([1, 2, 2, 3])
>>> s.replace_strict([1, 2, 3], [100, 200, 300])
shape: (4,)
Series: '' [i64]
[
        100
        200
        200
        300
]

Passing a mapping with replacements is also supported as syntactic sugar.

>>> mapping = {1: 100, 2: 200, 3: 300}
>>> s.replace_strict(mapping)
shape: (4,)
Series: '' [i64]
[
        100
        200
        200
        300
]

By default, an error is raised if any non-null values were not replaced. Specify a default to set all values that were not matched.

>>> mapping = {2: 200, 3: 300}
>>> s.replace_strict(mapping)  
Traceback (most recent call last):
...
polars.exceptions.InvalidOperationError: incomplete mapping specified for `replace_strict`
>>> s.replace_strict(mapping, default=-1)
shape: (4,)
Series: '' [i64]
[
        -1
        200
        200
        300
]

The default can be another Series.

>>> default = pl.Series([2.5, 5.0, 7.5, 10.0])
>>> s.replace_strict(2, 200, default=default)
shape: (4,)
Series: '' [f64]
[
        2.5
        200.0
        200.0
        10.0
]

Replacing by values of a different data type sets the return type based on a combination of the new data type and the default data type.

>>> s = pl.Series(["x", "y", "z"])
>>> mapping = {"x": 1, "y": 2, "z": 3}
>>> s.replace_strict(mapping)
shape: (3,)
Series: '' [i64]
[
        1
        2
        3
]
>>> s.replace_strict(mapping, default="x")
shape: (3,)
Series: '' [str]
[
        "1"
        "2"
        "3"
]

Set the return_dtype parameter to control the resulting data type directly.

>>> s.replace_strict(mapping, return_dtype=pl.UInt8)
shape: (3,)
Series: '' [u8]
[
        1
        2
        3
]

reshape(dimensions: tuple[int, ...]) → Series[source]

Reshape this Series to a flat Series or an Array Series.

Parameters:

dimensions: Tuple of the dimension sizes. If a -1 is used in any of the dimensions, that dimension is inferred.

Returns:

Series: If a single dimension is given, results in a Series of the original data type. If a multiple dimensions are given, results in a Series of data type Array with shape dimensions.

See also

Series.list.explode: Explode a list column.

Examples

>>> s = pl.Series("foo", [1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> square = s.reshape((3, 3))
>>> square
shape: (3,)
Series: 'foo' [array[i64, 3]]
[
        [1, 2, 3]
        [4, 5, 6]
        [7, 8, 9]
]
>>> square.reshape((9,))
shape: (9,)
Series: 'foo' [i64]
[
        1
        2
        3
        4
        5
        6
        7
        8
        9
]

reverse() → Series[source]

Return Series in reverse order.

Examples

>>> s = pl.Series("a", [1, 2, 3], dtype=pl.Int8)
>>> s.reverse()
shape: (3,)
Series: 'a' [i8]
[
    3
    2
    1
]

rle() → Series[source]

Compress the Series data using run-length encoding.

Run-length encoding (RLE) encodes data by storing each run of identical values as a single value and its length.

Returns:

Series: Series of data type Struct with fields len of data type UInt32 and value of the original data type.

Examples

>>> s = pl.Series("s", [1, 1, 2, 1, None, 1, 3, 3])
>>> s.rle().struct.unnest()
shape: (6, 2)
┌─────┬───────┐
│ len ┆ value │
│ --- ┆ ---   │
│ u32 ┆ i64   │
╞═════╪═══════╡
│ 2   ┆ 1     │
│ 1   ┆ 2     │
│ 1   ┆ 1     │
│ 1   ┆ null  │
│ 1   ┆ 1     │
│ 2   ┆ 3     │
└─────┴───────┘

rle_id() → Series[source]

Get a distinct integer ID for each run of identical values.

The ID starts at 0 and increases by one each time the value of the column changes.

Returns:

Series: Series of data type UInt32.

See also

rle

Notes

This functionality is especially useful for defining a new group for every time a column’s value changes, rather than for every distinct value of that column.

Examples

>>> s = pl.Series("s", [1, 1, 2, 1, None, 1, 3, 3])
>>> s.rle_id()
shape: (8,)
Series: 's' [u32]
[
    0
    0
    1
    2
    3
    4
    5
    5
]

rolling_map( function: Callable[[Series], Any], window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Compute a custom rolling window function.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

function: Custom aggregation function.
window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Warning

Computing custom functions is extremely slow. Use specialized rolling functions such as Series.rolling_sum() if at all possible.

Examples

>>> from numpy import nansum
>>> s = pl.Series([11.0, 2.0, 9.0, float("nan"), 8.0])
>>> s.rolling_map(nansum, window_size=3)
shape: (5,)
Series: '' [f64]
[
        null
        null
        22.0
        11.0
        17.0
]

rolling_max( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Apply a rolling max (moving max) over the values in this array.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their max.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [100, 200, 300, 400, 500])
>>> s.rolling_max(window_size=2)
shape: (5,)
Series: 'a' [i64]
[
    null
    200
    300
    400
    500
]

rolling_mean( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Apply a rolling mean (moving mean) over the values in this array.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their mean.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [100, 200, 300, 400, 500])
>>> s.rolling_mean(window_size=2)
shape: (5,)
Series: 'a' [f64]
[
    null
    150.0
    250.0
    350.0
    450.0
]

rolling_median( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Compute a rolling median.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, 4.0, 6.0, 8.0])
>>> s.rolling_median(window_size=3)
shape: (6,)
Series: 'a' [f64]
[
        null
        null
        2.0
        3.0
        4.0
        6.0
]

rolling_min( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Apply a rolling min (moving min) over the values in this array.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their min.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [100, 200, 300, 400, 500])
>>> s.rolling_min(window_size=3)
shape: (5,)
Series: 'a' [i64]
[
    null
    null
    100
    200
    300
]

rolling_quantile( quantile: float, interpolation: RollingInterpolationMethod = 'nearest', window_size: int = 2, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Compute a rolling quantile.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

quantile: Quantile between 0.0 and 1.0.
interpolation{‘nearest’, ‘higher’, ‘lower’, ‘midpoint’, ‘linear’}: Interpolation method.
window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, 4.0, 6.0, 8.0])
>>> s.rolling_quantile(quantile=0.33, window_size=3)
shape: (6,)
Series: 'a' [f64]
[
        null
        null
        1.0
        2.0
        3.0
        4.0
]
>>> s.rolling_quantile(quantile=0.33, interpolation="linear", window_size=3)
shape: (6,)
Series: 'a' [f64]
[
        null
        null
        1.66
        2.66
        3.66
        5.32
]

rolling_skew( window_size: int, *, bias: bool = True, ) → Series[source]

Compute a rolling skew.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

The window at a given row includes the row itself and the window_size - 1 elements before it.

Parameters:

window_size: Integer size of the rolling window.
bias: If False, the calculations are corrected for statistical bias.

Examples

>>> pl.Series([1, 4, 2, 9]).rolling_skew(3)
shape: (4,)
Series: '' [f64]
[
    null
    null
    0.381802
    0.47033
]

Note how the values match

>>> pl.Series([1, 4, 2]).skew(), pl.Series([4, 2, 9]).skew()
(0.38180177416060584, 0.47033046033698594)

rolling_std( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ddof: int = 1, ) → Series[source]

Compute a rolling std dev.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their std dev.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.
ddof: “Delta Degrees of Freedom”: The divisor for a length N window is N - ddof

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, 4.0, 6.0, 8.0])
>>> s.rolling_std(window_size=3)
shape: (6,)
Series: 'a' [f64]
[
        null
        null
        1.0
        1.0
        1.527525
        2.0
]

rolling_sum( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ) → Series[source]

Apply a rolling sum (moving sum) over the values in this array.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their sum.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.rolling_sum(window_size=2)
shape: (5,)
Series: 'a' [i64]
[
        null
        3
        5
        7
        9
]

rolling_var( window_size: int, weights: list[float] | None = None, *, min_periods: int | None = None, center: bool = False, ddof: int = 1, ) → Series[source]

Compute a rolling variance.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the array. The values that fill this window will (optionally) be multiplied with the weights given by the weight vector. The resulting values will be aggregated to their variance.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

window_size: The length of the window in number of elements.
weights: An optional slice with the same length as the window that will be multiplied elementwise with the values in the window.
min_periods: The number of values in the window that should be non-null before computing a result. If set to None (default), it will be set equal to window_size.
center: Set the labels at the center of the window.
ddof: “Delta Degrees of Freedom”: The divisor for a length N window is N - ddof

Examples

>>> s = pl.Series("a", [1.0, 2.0, 3.0, 4.0, 6.0, 8.0])
>>> s.rolling_var(window_size=3)
shape: (6,)
Series: 'a' [f64]
[
        null
        null
        1.0
        1.0
        2.333333
        4.0
]

round(decimals: int = 0) → Series[source]

Round underlying floating point data by decimals digits.

Parameters:

decimals: number of decimals to round by.

Examples

>>> s = pl.Series("a", [1.12345, 2.56789, 3.901234])
>>> s.round(2)
shape: (3,)
Series: 'a' [f64]
[
        1.12
        2.57
        3.9
]

round_sig_figs(digits: int) → Series[source]

Round to a number of significant figures.

Parameters:

digits: Number of significant figures to round to.

Examples

>>> s = pl.Series([0.01234, 3.333, 1234.0])
>>> s.round_sig_figs(2)
shape: (3,)
Series: '' [f64]
[
        0.012
        3.3
        1200.0
]

sample( n: int | None = None, *, fraction: float | None = None, with_replacement: bool = False, shuffle: bool = False, seed: int | None = None, ) → Series[source]

Sample from this Series.

Parameters:

n: Number of items to return. Cannot be used with fraction. Defaults to 1 if fraction is None.
fraction: Fraction of items to return. Cannot be used with n.
with_replacement: Allow values to be sampled more than once.
shuffle: Shuffle the order of sampled data points.
seed: Seed for the random number generator. If set to None (default), a random seed is generated for each sample operation.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.sample(2, seed=0)  
shape: (2,)
Series: 'a' [i64]
[
    1
    5
]

Set values at the index locations.

Parameters:

indices: Integers representing the index locations.
values: Replacement values.

Notes

Use of this function is frequently an anti-pattern, as it can block optimization (predicate pushdown, etc). Consider using pl.when(predicate).then(value).otherwise(self) instead.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.scatter(1, 10)
shape: (3,)
Series: 'a' [i64]
[
        1
        10
        3
]

It is better to implement this as follows:

>>> s.to_frame().with_row_index().select(
...     pl.when(pl.col("index") == 1).then(10).otherwise(pl.col("a"))
... )
shape: (3, 1)
┌─────────┐
│ literal │
│ ---     │
│ i64     │
╞═════════╡
│ 1       │
│ 10      │
│ 3       │
└─────────┘

search_sorted( element: IntoExpr | np.ndarray[Any, Any] | None, side: SearchSortedSide = 'any', ) → int | Series[source]

Find indices where elements should be inserted to maintain order.

\[a[i-1] < v <= a[i]\]

Parameters:

element: Expression or scalar value.
side{‘any’, ‘left’, ‘right’}: If ‘any’, the index of the first suitable location found is given. If ‘left’, the index of the leftmost suitable location found is given. If ‘right’, return the rightmost suitable location found is given.

Examples

>>> s = pl.Series("set", [1, 2, 3, 4, 4, 5, 6, 7])
>>> s.search_sorted(4)
3
>>> s.search_sorted(4, "left")
3
>>> s.search_sorted(4, "right")
5
>>> s.search_sorted([1, 4, 5])
shape: (3,)
Series: 'set' [u32]
[
        0
        3
        5
]
>>> s.search_sorted([1, 4, 5], "left")
shape: (3,)
Series: 'set' [u32]
[
        0
        3
        5
]
>>> s.search_sorted([1, 4, 5], "right")
shape: (3,)
Series: 'set' [u32]
[
        1
        5
        6
]

set( filter: Series, value: int | float | str | bool | None, ) → Series[source]

Set masked values.

Parameters:

filter: Boolean mask.
value: Value with which to replace the masked values.

Notes

Use of this function is frequently an anti-pattern, as it can block optimisation (predicate pushdown, etc). Consider using pl.when(predicate).then(value).otherwise(self) instead.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.set(s == 2, 10)
shape: (3,)
Series: 'a' [i64]
[
        1
        10
        3
]

It is better to implement this as follows:

>>> s.to_frame().select(
...     pl.when(pl.col("a") == 2).then(10).otherwise(pl.col("a"))
... )
shape: (3, 1)
┌─────────┐
│ literal │
│ ---     │
│ i64     │
╞═════════╡
│ 1       │
│ 10      │
│ 3       │
└─────────┘

set_sorted(*, descending: bool = False) → Self[source]

Flags the Series as ‘sorted’.

Enables downstream code to user fast paths for sorted arrays.

Parameters:

descending: If the Series order is descending.

Warning

This can lead to incorrect results if this Series is not sorted!! Use with care!

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.set_sorted().max()
3

property shape: tuple[int][source]

Shape of this Series.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.shape
(3,)

shift(n: int = 1, *, fill_value: IntoExpr | None = None) → Series[source]

Shift values by the given number of indices.

Parameters:

n: Number of indices to shift forward. If a negative value is passed, values are shifted in the opposite direction instead.
fill_value: Fill the resulting null values with this value. Accepts expression input. Non-expression inputs are parsed as literals.

Notes

This method is similar to the LAG operation in SQL when the value for n is positive. With a negative value for n, it is similar to LEAD.

Examples

By default, values are shifted forward by one index.

>>> s = pl.Series([1, 2, 3, 4])
>>> s.shift()
shape: (4,)
Series: '' [i64]
[
        null
        1
        2
        3
]

Pass a negative value to shift in the opposite direction instead.

>>> s.shift(-2)
shape: (4,)
Series: '' [i64]
[
        3
        4
        null
        null
]

Specify fill_value to fill the resulting null values.

>>> s.shift(-2, fill_value=100)
shape: (4,)
Series: '' [i64]
[
        3
        4
        100
        100
]

shrink_dtype() → Series[source]

Shrink numeric columns to the minimal required datatype.

Shrink to the dtype needed to fit the extrema of this [Series]. This can be used to reduce memory pressure.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5, 6])
>>> s
shape: (6,)
Series: 'a' [i64]
[
        1
        2
        3
        4
        5
        6
]
>>> s.shrink_dtype()
shape: (6,)
Series: 'a' [i8]
[
        1
        2
        3
        4
        5
        6
]

shrink_to_fit(*, in_place: bool = False) → Series[source]

Shrink Series memory usage.

Shrinks the underlying array capacity to exactly fit the actual data. (Note that this function does not change the Series data type).

shuffle(seed: int | None = None) → Series[source]

Shuffle the contents of this Series.

Parameters:

seed: Seed for the random number generator. If set to None (default), a random seed is generated each time the shuffle is called.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.shuffle(seed=1)
shape: (3,)
Series: 'a' [i64]
[
        2
        1
        3
]

sign() → Series[source]

Compute the element-wise indication of the sign.

The returned values can be -1, 0, or 1:

-1 if x < 0.
0 if x == 0.
1 if x > 0.

(null values are preserved as-is).

Examples

>>> s = pl.Series("a", [-9.0, -0.0, 0.0, 4.0, None])
>>> s.sign()
shape: (5,)
Series: 'a' [i64]
[
        -1
        0
        0
        1
        null
]

sin() → Series[source]

Compute the element-wise value for the sine.

Examples

>>> import math
>>> s = pl.Series("a", [0.0, math.pi / 2.0, math.pi])
>>> s.sin()
shape: (3,)
Series: 'a' [f64]
[
    0.0
    1.0
    1.2246e-16
]

sinh() → Series[source]

Compute the element-wise value for the hyperbolic sine.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.sinh()
shape: (3,)
Series: 'a' [f64]
[
    1.175201
    0.0
    -1.175201
]

skew(*, bias: bool = True) → float | None[source]

Compute the sample skewness of a data set.

For normally distributed data, the skewness should be about zero. For unimodal continuous distributions, a skewness value greater than zero means that there is more weight in the right tail of the distribution. The function skewtest can be used to determine if the skewness value is close enough to zero, statistically speaking.

See scipy.stats for more information.

Parameters:

biasbool, optional: If False, the calculations are corrected for statistical bias.

Notes

The sample skewness is computed as the Fisher-Pearson coefficient of skewness, i.e.

\[g_1=\frac{m_3}{m_2^{3/2}}\]

where

\[m_i=\frac{1}{N}\sum_{n=1}^N(x[n]-\bar{x})^i\]

is the biased sample \(i\texttt{th}\) central moment, and \(\bar{x}\) is the sample mean. If bias is False, the calculations are corrected for bias and the value computed is the adjusted Fisher-Pearson standardized moment coefficient, i.e.

\[G_1 = \frac{k_3}{k_2^{3/2}} = \frac{\sqrt{N(N-1)}}{N-2}\frac{m_3}{m_2^{3/2}}\]

Examples

>>> s = pl.Series([1, 2, 2, 4, 5])
>>> s.skew()
0.34776706224699483

slice(offset: int, length: int | None = None) → Series[source]

Get a slice of this Series.

Parameters:

offset: Start index. Negative indexing is supported.
length: Length of the slice. If set to None, all rows starting at the offset will be selected.

Examples

>>> s = pl.Series("a", [1, 2, 3, 4])
>>> s.slice(1, 2)
shape: (2,)
Series: 'a' [i64]
[
        2
        3
]

sort( *, descending: bool = False, nulls_last: bool = False, multithreaded: bool = True, in_place: bool = False, ) → Self[source]

Sort this Series.

Parameters:

descending: Sort in descending order.
nulls_last: Place null values last instead of first.
multithreaded: Sort using multiple threads.
in_place: Sort in-place.

Examples

>>> s = pl.Series("a", [1, 3, 4, 2])
>>> s.sort()
shape: (4,)
Series: 'a' [i64]
[
        1
        2
        3
        4
]
>>> s.sort(descending=True)
shape: (4,)
Series: 'a' [i64]
[
        4
        3
        2
        1
]

sqrt() → Series[source]

Compute the square root of the elements.

Syntactic sugar for

>>> pl.Series([1, 2]) ** 0.5
shape: (2,)
Series: '' [f64]
[
    1.0
    1.414214
]

Examples

>>> s = pl.Series([1, 2, 3])
>>> s.sqrt()
shape: (3,)
Series: '' [f64]
[
    1.0
    1.414214
    1.732051
]

std(ddof: int = 1) → float | timedelta | None[source]

Get the standard deviation of this Series.

Parameters:

ddof: “Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.std()
1.0

sum() → int | float[source]

Reduce this Series to the sum value.

Notes

Dtypes in {Int8, UInt8, Int16, UInt16} are cast to Int64 before summing to prevent overflow issues.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.sum()
6

tail(n: int = 10) → Series[source]

Get the last n elements.

Parameters:

n: Number of elements to return. If a negative value is passed, return all elements except the first abs(n).

See also

head, slice

Examples

>>> s = pl.Series("a", [1, 2, 3, 4, 5])
>>> s.tail(3)
shape: (3,)
Series: 'a' [i64]
[
        3
        4
        5
]

Pass a negative value to get all rows except the first abs(n).

>>> s.tail(-3)
shape: (2,)
Series: 'a' [i64]
[
        4
        5
]

tan() → Series[source]

Compute the element-wise value for the tangent.

Examples

>>> import math
>>> s = pl.Series("a", [0.0, math.pi / 2.0, math.pi])
>>> s.tan()
shape: (3,)
Series: 'a' [f64]
[
    0.0
    1.6331e16
    -1.2246e-16
]

tanh() → Series[source]

Compute the element-wise value for the hyperbolic tangent.

Examples

>>> s = pl.Series("a", [1.0, 0.0, -1.0])
>>> s.tanh()
shape: (3,)
Series: 'a' [f64]
[
    0.761594
    0.0
    -0.761594
]

to_arrow( *, compat_level: CompatLevel | None = None, ) → Array[source]

Return the underlying Arrow array.

If the Series contains only a single chunk this operation is zero copy.

Parameters:

compat_level: Use a specific compatibility level when exporting Polars’ internal data structures.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s = s.to_arrow()
>>> s  
<pyarrow.lib.Int64Array object at ...>
[
  1,
  2,
  3
]

to_dummies(*, separator: str = '_', drop_first: bool = False) → DataFrame[source]

Get dummy/indicator variables.

Parameters:

separator: Separator/delimiter used when generating column names.
drop_first: Remove the first category from the variable being encoded.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.to_dummies()
shape: (3, 3)
┌─────┬─────┬─────┐
│ a_1 ┆ a_2 ┆ a_3 │
│ --- ┆ --- ┆ --- │
│ u8  ┆ u8  ┆ u8  │
╞═════╪═════╪═════╡
│ 1   ┆ 0   ┆ 0   │
│ 0   ┆ 1   ┆ 0   │
│ 0   ┆ 0   ┆ 1   │
└─────┴─────┴─────┘

>>> s.to_dummies(drop_first=True)
shape: (3, 2)
┌─────┬─────┐
│ a_2 ┆ a_3 │
│ --- ┆ --- │
│ u8  ┆ u8  │
╞═════╪═════╡
│ 0   ┆ 0   │
│ 1   ┆ 0   │
│ 0   ┆ 1   │
└─────┴─────┘

to_frame(name: str | None = None) → DataFrame[source]

Cast this Series to a DataFrame.

Parameters:

name: optionally name/rename the Series column in the new DataFrame.

Examples

>>> s = pl.Series("a", [123, 456])
>>> df = s.to_frame()
>>> df
shape: (2, 1)
┌─────┐
│ a   │
│ --- │
│ i64 │
╞═════╡
│ 123 │
│ 456 │
└─────┘

>>> df = s.to_frame("xyz")
>>> df
shape: (2, 1)
┌─────┐
│ xyz │
│ --- │
│ i64 │
╞═════╡
│ 123 │
│ 456 │
└─────┘

to_init_repr(n: int = 1000) → str[source]

Convert Series to instantiatable string representation.

Parameters:

n: Only use first n elements.

See also

polars.Series.to_init_repr
polars.from_repr

Examples

>>> s = pl.Series("a", [1, 2, None, 4], dtype=pl.Int16)
>>> print(s.to_init_repr())
pl.Series('a', [1, 2, None, 4], dtype=pl.Int16)
>>> s_from_str_repr = eval(s.to_init_repr())
>>> s_from_str_repr
shape: (4,)
Series: 'a' [i16]
[
    1
    2
    null
    4
]

to_jax(device: jax.Device | str | None = None) → jax.Array[source]

Convert this Series to a Jax Array.

Added in version 0.20.27.

Warning

This functionality is currently considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

device: Specify the jax Device on which the array will be created; can provide a string (such as “cpu”, “gpu”, or “tpu”) in which case the device is retrieved as jax.devices(string)[0]. For more specific control you can supply the instantiated Device directly. If None, arrays are created on the default device.

Examples

>>> s = pl.Series("x", [10.5, 0.0, -10.0, 5.5])
>>> s.to_jax()
Array([ 10.5,   0. , -10. ,   5.5], dtype=float32)

to_list() → list[Any][source]

Convert this Series to a Python list.

This operation copies data.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.to_list()
[1, 2, 3]
>>> type(s.to_list())
<class 'list'>

to_numpy( *, writable: bool = False, allow_copy: bool = True, use_pyarrow: bool | None = None, zero_copy_only: bool | None = None, ) → ndarray[Any, Any][source]

Convert this Series to a NumPy ndarray.

This operation copies data only when necessary. The conversion is zero copy when all of the following hold:

The data type is an integer, float, Datetime, Duration, or Array.
The Series contains no null values.
The Series consists of a single chunk.
The writable parameter is set to False (default).

Parameters:

writable: Ensure the resulting array is writable. This will force a copy of the data if the array was created without copy as the underlying Arrow data is immutable.
allow_copy: Allow memory to be copied to perform the conversion. If set to False, causes conversions that are not zero-copy to fail.
use_pyarrow: First convert to PyArrow, then call pyarrow.Array.to_numpy to convert to NumPy. If set to False, Polars’ own conversion logic is used.

Deprecated since version 0.20.28: Polars now uses its native engine by default for conversion to NumPy. To use PyArrow’s engine, call .to_arrow().to_numpy() instead.
zero_copy_only: Raise an exception if the conversion to a NumPy would require copying the underlying data. Data copy occurs, for example, when the Series contains nulls or non-numeric types.

Deprecated since version 0.20.10: Use the allow_copy parameter instead, which is the inverse of this one.

Examples

Numeric data without nulls can be converted without copying data. The resulting array will not be writable.

>>> s = pl.Series([1, 2, 3], dtype=pl.Int8)
>>> arr = s.to_numpy()
>>> arr
array([1, 2, 3], dtype=int8)
>>> arr.flags.writeable
False

Set writable=True to force data copy to make the array writable.

>>> s.to_numpy(writable=True).flags.writeable
True

Integer Series containing nulls will be cast to a float type with nan representing a null value. This requires data to be copied.

>>> s = pl.Series([1, 2, None], dtype=pl.UInt16)
>>> s.to_numpy()
array([ 1.,  2., nan], dtype=float32)

Set allow_copy=False to raise an error if data would be copied.

>>> s.to_numpy(allow_copy=False)  
Traceback (most recent call last):
...
RuntimeError: copy not allowed: cannot convert to a NumPy array without copying data

Series of data type Array and Struct will result in an array with more than one dimension.

>>> s = pl.Series([[1, 2, 3], [4, 5, 6]], dtype=pl.Array(pl.Int64, 3))
>>> s.to_numpy()
array([[1, 2, 3],
       [4, 5, 6]])

to_pandas(

*,

use_pyarrow_extension_array: bool = False,

**kwargs: Any,

) → pd.Series[Any][source]

Convert this Series to a pandas Series.

This operation copies data if use_pyarrow_extension_array is not enabled.

Parameters:

use_pyarrow_extension_array: Use a PyArrow-backed extension array instead of a NumPy array for the pandas Series. This allows zero copy operations and preservation of null values. Subsequent operations on the resulting pandas Series may trigger conversion to NumPy if those operations are not supported by PyArrow compute functions.
**kwargs: Additional keyword arguments to be passed to pyarrow.Array.to_pandas().

Returns:

pandas.Series

Notes

This operation requires that both pandas and pyarrow are installed.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.to_pandas()
0    1
1    2
2    3
Name: a, dtype: int64

Null values are converted to NaN.

>>> s = pl.Series("b", [1, 2, None])
>>> s.to_pandas()
0    1.0
1    2.0
2    NaN
Name: b, dtype: float64

Pass use_pyarrow_extension_array=True to get a pandas Series backed by a PyArrow extension array. This will preserve null values.

>>> s.to_pandas(use_pyarrow_extension_array=True)
0       1
1       2
2    <NA>
Name: b, dtype: int64[pyarrow]

to_physical() → Series[source]

Cast to physical representation of the logical dtype.

polars.datatypes.Date() -> polars.datatypes.Int32()
polars.datatypes.Datetime() -> polars.datatypes.Int64()
polars.datatypes.Time() -> polars.datatypes.Int64()
polars.datatypes.Duration() -> polars.datatypes.Int64()
polars.datatypes.Categorical() -> polars.datatypes.UInt32()
List(inner) -> List(physical of inner)
Other data types will be left unchanged.

Examples

Replicating the pandas pd.Series.factorize method.

>>> s = pl.Series("values", ["a", None, "x", "a"])
>>> s.cast(pl.Categorical).to_physical()
shape: (4,)
Series: 'values' [u32]
[
    0
    null
    1
    0
]

to_torch() → torch.Tensor[source]

Convert this Series to a PyTorch Tensor.

Added in version 0.20.23.

Warning

This functionality is currently considered unstable. It may be changed at any point without it being considered a breaking change.

Notes

PyTorch tensors do not support UInt16, UInt32, or UInt64; these dtypes will be automatically cast to Int32, Int64, and Int64, respectively.

Examples

>>> s = pl.Series("x", [1, 0, 1, 2, 0], dtype=pl.UInt8)
>>> s.to_torch()
tensor([1, 0, 1, 2, 0], dtype=torch.uint8)
>>> s = pl.Series("x", [5.5, -10.0, 2.5], dtype=pl.Float32)
>>> s.to_torch()
tensor([  5.5000, -10.0000,   2.5000])

top_k(k: int = 5) → Series[source]

Return the k largest elements.

Non-null elements are always preferred over null elements. The output is not guaranteed to be in any particular order, call sort() after this function if you wish the output to be sorted.

This has time complexity:

\[O(n)\]

Parameters:

k: Number of elements to return.

See also

bottom_k

Examples

>>> s = pl.Series("a", [2, 5, 1, 4, 3])
>>> s.top_k(3)
shape: (3,)
Series: 'a' [i64]
[
    5
    4
    3
]

unique(*, maintain_order: bool = False) → Series[source]

Get unique elements in series.

Parameters:

maintain_order: Maintain order of data. This requires more work.

Examples

>>> s = pl.Series("a", [1, 2, 2, 3])
>>> s.unique().sort()
shape: (3,)
Series: 'a' [i64]
[
    1
    2
    3
]

unique_counts() → Series[source]

Return a count of the unique values in the order of appearance.

Examples

>>> s = pl.Series("id", ["a", "b", "b", "c", "c", "c"])
>>> s.unique_counts()
shape: (3,)
Series: 'id' [u32]
[
    1
    2
    3
]

upper_bound() → Self[source]

Return the upper bound of this Series’ dtype as a unit Series.

See also

lower_bound: return the lower bound of the given Series’ dtype.

Examples

>>> s = pl.Series("s", [-1, 0, 1], dtype=pl.Int8)
>>> s.upper_bound()
shape: (1,)
Series: 's' [i8]
[
    127
]

>>> s = pl.Series("s", [1.0, 2.5, 3.0], dtype=pl.Float64)
>>> s.upper_bound()
shape: (1,)
Series: 's' [f64]
[
    inf
]

value_counts( *, sort: bool = False, parallel: bool = False, name: str | None = None, normalize: bool = False, ) → DataFrame[source]

Count the occurrences of unique values.

Parameters:

sort: Sort the output by count in descending order. If set to False (default), the order of the output is random.
parallel: Execute the computation in parallel.

Note

This option should likely not be enabled in a group by context, as the computation is already parallelized per group.
name: Give the resulting count column a specific name; if normalize is True defaults to “proportion”, otherwise defaults to “count”.
normalize: If true gives relative frequencies of the unique values

Returns:

DataFrame: Mapping of unique values to their count.

Examples

>>> s = pl.Series("color", ["red", "blue", "red", "green", "blue", "blue"])
>>> s.value_counts()  
shape: (3, 2)
┌───────┬───────┐
│ color ┆ count │
│ ---   ┆ ---   │
│ str   ┆ u32   │
╞═══════╪═══════╡
│ red   ┆ 2     │
│ green ┆ 1     │
│ blue  ┆ 3     │
└───────┴───────┘

Sort the output by count and customize the count column name.

>>> s.value_counts(sort=True, name="n")
shape: (3, 2)
┌───────┬─────┐
│ color ┆ n   │
│ ---   ┆ --- │
│ str   ┆ u32 │
╞═══════╪═════╡
│ blue  ┆ 3   │
│ red   ┆ 2   │
│ green ┆ 1   │
└───────┴─────┘

var(ddof: int = 1) → float | timedelta | None[source]

Get variance of this Series.

Parameters:

ddof: “Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

Examples

>>> s = pl.Series("a", [1, 2, 3])
>>> s.var()
1.0

zip_with(mask: Series, other: Series) → Self[source]

Take values from self or other based on the given mask.

Where mask evaluates true, take values from self. Where mask evaluates false, take values from other.

Parameters:

mask: Boolean Series.
other: Series of same type.

Returns:

Series

Examples

>>> s1 = pl.Series([1, 2, 3, 4, 5])
>>> s2 = pl.Series([5, 4, 3, 2, 1])
>>> s1.zip_with(s1 < s2, s2)
shape: (5,)
Series: '' [i64]
[
        1
        2
        3
        2
        1
]
>>> mask = pl.Series([True, False, True, False, True])
>>> s1.zip_with(mask, s2)
shape: (5,)
Series: '' [i64]
[
        1
        4
        3
        2
        5
]