polars.datatypes.Map

class polars.datatypes.Map(key: PolarsDataType | PythonDataType, value: PolarsDataType | PythonDataType)

Key-value mapping type.

Keys are unique within a row and never null. Entry order is preserved and participates in equality and hashing.

Duplicate keys are resolved when a map is built, keeping the first position and the last value.

Parameters:

key

The DataType of the keys. Must be row-encodable, so Object is not allowed.

A nested key dtype is accepted by Polars but has no Python representation.

value

The DataType of the values.

Examples

>>> s = pl.Series("a", [{"x": 1, "y": 2}], dtype=pl.Map(pl.String, pl.Int64))
>>> s
shape: (1,)
Series: 'a' [map[str, i64]]
[
        {"x": 1, "y": 2}
]

__init__(

key: PolarsDataType | PythonDataType,

value: PolarsDataType | PythonDataType,

) → None

Methods

__init__(key, value)
base_type()	Return this DataType's fundamental/root type class.
from_python(py_type)	Return the Polars data type corresponding to a given Python type.
is_(other)	Check if this DataType is the same as another DataType.
is_decimal()	Check whether the data type is a decimal type.
is_extension()	Check whether the data type is an extension type.
is_float()	Check whether the data type is a floating point type.
is_integer()	Check whether the data type is an integer type.
is_nested()	Check whether the data type is a nested type.
is_numeric()	Check whether the data type is a numeric type.
is_object()	Check whether the data type is an object type.
is_signed_integer()	Check whether the data type is a signed integer type.
is_temporal()	Check whether the data type is a temporal type.
is_unsigned_integer()	Check whether the data type is an unsigned integer type.
to_dtype_expr()	Return a DataTypeExpr with a static DataType.
to_python()	Return the Python type corresponding to this Polars data type.

Attributes

key
value