file: str | Path | IO[str] | IO[bytes] | None = None,
include_bom: bool = False,
include_header: bool = True,
separator: str = ',',
line_terminator: str = '\n',
quote_char: str = '"',
batch_size: int = 1024,
datetime_format: str | None = None,
date_format: str | None = None,
time_format: str | None = None,
float_precision: int | None = None,
null_value: str | None = None,
quote_style: CsvQuoteStyle | None = None,
) str | None[source]#

Write to comma-separated values (CSV) file.


File path or writable file-like object to which the result will be written. If set to None (default), the output is returned as a string instead.


Whether to include UTF-8 BOM in the CSV output.


Whether to include header in the CSV output.


Separate CSV fields with this symbol.


String used to end each row.


Byte to use as quoting character.


Number of rows that will be processed per thread.


A format string, with the specifiers defined by the chrono Rust crate. If no format specified, the default fractional-second precision is inferred from the maximum timeunit found in the frame’s Datetime cols (if any).


A format string, with the specifiers defined by the chrono Rust crate.


A format string, with the specifiers defined by the chrono Rust crate.


Number of decimal places to write, applied to both Float32 and Float64 datatypes.


A string representing null values (defaulting to the empty string).

quote_style{‘necessary’, ‘always’, ‘non_numeric’, ‘never’}

Determines the quoting strategy used.

  • necessary (default): This puts quotes around fields only when necessary. They are necessary when fields contain a quote, separator or record terminator. Quotes are also necessary when writing an empty record (which is indistinguishable from a record with one empty field). This is the default.

  • always: This puts quotes around every field. Always.

  • never: This never puts quotes around fields, even if that results in invalid CSV data (e.g.: by not quoting strings containing the separator).

  • non_numeric: This puts quotes around all fields that are non-numeric. Namely, when writing a field that does not parse as a valid float or integer, then quotes will be used even if they aren`t strictly necessary.


>>> import pathlib
>>> df = pl.DataFrame(
...     {
...         "foo": [1, 2, 3, 4, 5],
...         "bar": [6, 7, 8, 9, 10],
...         "ham": ["a", "b", "c", "d", "e"],
...     }
... )
>>> path: pathlib.Path = dirpath / "new_file.csv"
>>> df.write_csv(path, separator=",")