Struct polars::prelude::LazyCsvReader

pub struct LazyCsvReader { /* private fields */ }

Available on crate features lazy and csv only.

Implementations

impl LazyCsvReader

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

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

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

Skip this number of rows after the header location.

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

Add a row index column.

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

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

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

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.

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

Continue with next batch when a ParserError is encountered.

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

Set the CSV file’s schema

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

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

pub fn with_dtype_overwrite(self, schema: Option<Arc<Schema>>) -> LazyCsvReader

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

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

Set whether the CSV file has headers

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

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

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

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

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

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

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

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

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

Set values that will be interpreted as missing/ null.

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

Treat missing fields as null.

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

Cache the DataFrame after reading.

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

Reduce memory usage at the expense of performance

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

Set CsvEncoding

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

Available on crate feature temporal only.

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

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

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

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

Truncate lines that are longer than the schema.

pub fn with_decimal_comma(self, toggle: bool) -> LazyCsvReader

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

where F: Fn(Schema) -> Result<Schema, PolarsError>,

Modify a schema before we run the lazy scanning.

Important! Run this function latest in the builder!

Trait Implementations

impl Clone for LazyCsvReader

fn clone(&self) -> LazyCsvReader

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl LazyFileListReader for LazyCsvReader

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

Rechunk the memory to contiguous chunks when parsing is done.

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.

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

Return the row index settings.

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

Get the final LazyFrame. This method assumes, that path is not a glob.

fn path(&self) -> &Path

Path of the scanned file. It can be potentially a glob pattern.

fn paths(&self) -> &[PathBuf]

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

Set path of the scanned file. Support glob patterns.

fn with_paths(self, paths: Arc<[PathBuf]>) -> LazyCsvReader

Set paths of the scanned files. Doesn’t glob patterns.

fn with_n_rows(self, n_rows: impl Into<Option<usize>>) -> LazyCsvReader

Configure the row limit.

fn with_row_index(self, row_index: impl Into<Option<RowIndex>>) -> LazyCsvReader

Configure the row index.

fn rechunk(&self) -> bool

Rechunk the memory to contiguous chunks when parsing is done.

fn concat_impl(&self, lfs: Vec<LazyFrame>) -> Result<LazyFrame, PolarsError>

Recommended concatenation of LazyFrames from many input files.

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

Get the final LazyFrame.

fn cloud_options(&self) -> Option<&CloudOptions>

CloudOptions used to list files.

fn iter_paths( &self ) -> Result<Option<Box<dyn Iterator<Item = Result<PathBuf, PolarsError>>>>, PolarsError>

Get list of files referenced by this reader.