Struct polars::prelude::LazyCsvReader

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pub struct LazyCsvReader<'a> { /* private fields */ }
Available on crate features lazy and csv only.

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impl<'a> LazyCsvReader<'a>

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pub fn new_paths(paths: Arc<[PathBuf]>) -> LazyCsvReader<'a>

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pub fn new(path: impl AsRef<Path>) -> LazyCsvReader<'a>

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pub fn with_skip_rows_after_header(self, offset: usize) -> LazyCsvReader<'a>

Skip this number of rows after the header location.

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pub fn with_row_index(self, row_index: Option<RowIndex>) -> LazyCsvReader<'a>

Add a row index column.

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pub fn with_n_rows(self, num_rows: Option<usize>) -> LazyCsvReader<'a>

Try to stop parsing when n rows are parsed. During multithreaded parsing the upper bound n cannot be guaranteed.

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pub fn with_infer_schema_length( self, num_rows: Option<usize> ) -> LazyCsvReader<'a>

Set the number of rows to use when inferring the csv schema. the default is 100 rows. Setting to None will do a full table scan, very slow.

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pub fn with_ignore_errors(self, ignore: bool) -> LazyCsvReader<'a>

Continue with next batch when a ParserError is encountered.

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pub fn with_schema(self, schema: Option<Arc<Schema>>) -> LazyCsvReader<'a>

Set the CSV file’s schema

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pub fn with_skip_rows(self, skip_rows: usize) -> LazyCsvReader<'a>

Skip the first n rows during parsing. The header will be parsed at row n.

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pub fn with_dtype_overwrite( self, schema: Option<&'a Schema> ) -> LazyCsvReader<'a>

Overwrite the schema with the dtypes in this given Schema. The given schema may be a subset of the total schema.

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pub fn has_header(self, has_header: bool) -> LazyCsvReader<'a>

Set whether the CSV file has headers

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pub fn with_separator(self, separator: u8) -> LazyCsvReader<'a>

Set the CSV file’s column separator as a byte character

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pub fn with_comment_prefix( self, comment_prefix: Option<&str> ) -> LazyCsvReader<'a>

Set the comment prefix for this instance. Lines starting with this prefix will be ignored.

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pub fn with_quote_char(self, quote: Option<u8>) -> LazyCsvReader<'a>

Set the char used as quote char. The default is b'"'. If set to [None] quoting is disabled.

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pub fn with_end_of_line_char(self, eol_char: u8) -> LazyCsvReader<'a>

Set the char used as end of line. The default is b'\n'.

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pub fn with_null_values( self, null_values: Option<NullValues> ) -> LazyCsvReader<'a>

Set values that will be interpreted as missing/ null.

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pub fn with_missing_is_null(self, missing_is_null: bool) -> LazyCsvReader<'a>

Treat missing fields as null.

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pub fn with_cache(self, cache: bool) -> LazyCsvReader<'a>

Cache the DataFrame after reading.

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pub fn low_memory(self, toggle: bool) -> LazyCsvReader<'a>

Reduce memory usage at the expense of performance

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pub fn with_encoding(self, enc: CsvEncoding) -> LazyCsvReader<'a>

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pub fn with_try_parse_dates(self, toggle: bool) -> LazyCsvReader<'a>

Available on crate feature temporal only.

Automatically try to parse dates/datetimes and time. If parsing fails, columns remain of dtype [DataType::String].

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pub fn raise_if_empty(self, toggle: bool) -> LazyCsvReader<'a>

Raise an error if CSV is empty (otherwise return an empty frame)

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pub fn truncate_ragged_lines(self, toggle: bool) -> LazyCsvReader<'a>

Truncate lines that are longer than the schema.

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pub fn with_schema_modify<F>( self, f: F ) -> Result<LazyCsvReader<'a>, PolarsError>

Modify a schema before we run the lazy scanning.

Important! Run this function latest in the builder!

Trait Implementations§

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impl<'a> Clone for LazyCsvReader<'a>

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fn clone(&self) -> LazyCsvReader<'a>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl LazyFileListReader for LazyCsvReader<'_>

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fn with_rechunk(self, toggle: bool) -> LazyCsvReader<'_>

Rechunk the memory to contiguous chunks when parsing is done.

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fn n_rows(&self) -> Option<usize>

Try to stop parsing when n rows are parsed. During multithreaded parsing the upper bound n cannot be guaranteed.

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fn row_index(&self) -> Option<&RowIndex>

Return the row index settings.

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fn finish_no_glob(self) -> Result<LazyFrame, PolarsError>

Get the final LazyFrame. This method assumes, that path is not a glob. Read more
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fn path(&self) -> &Path

Path of the scanned file. It can be potentially a glob pattern.
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fn paths(&self) -> &[PathBuf]

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fn with_path(self, path: PathBuf) -> LazyCsvReader<'_>

Set path of the scanned file. Support glob patterns.
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fn with_paths(self, paths: Arc<[PathBuf]>) -> LazyCsvReader<'_>

Set paths of the scanned files. Doesn’t glob patterns.
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fn with_n_rows(self, n_rows: impl Into<Option<usize>>) -> LazyCsvReader<'_>

Configure the row limit.
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fn with_row_index( self, row_index: impl Into<Option<RowIndex>> ) -> LazyCsvReader<'_>

Configure the row index.
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fn rechunk(&self) -> bool

Rechunk the memory to contiguous chunks when parsing is done.
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fn concat_impl(&self, lfs: Vec<LazyFrame>) -> Result<LazyFrame, PolarsError>

Recommended concatenation of LazyFrames from many input files. Read more
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fn finish(self) -> Result<LazyFrame, PolarsError>

Get the final LazyFrame.
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fn cloud_options(&self) -> Option<&CloudOptions>

CloudOptions used to list files.
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fn iter_paths( &self ) -> Result<Option<Box<dyn Iterator<Item = Result<PathBuf, PolarsError>>>>, PolarsError>

Get list of files referenced by this reader. Read more

Auto Trait Implementations§

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impl<'a> Freeze for LazyCsvReader<'a>

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impl<'a> !RefUnwindSafe for LazyCsvReader<'a>

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impl<'a> Send for LazyCsvReader<'a>

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impl<'a> Sync for LazyCsvReader<'a>

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impl<'a> Unpin for LazyCsvReader<'a>

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impl<'a> !UnwindSafe for LazyCsvReader<'a>

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> DynClone for T
where T: Clone,

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fn __clone_box(&self, _: Private) -> *mut ()

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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V