polars.read_parquet#
- polars.read_parquet(
- source: str | Path | BinaryIO | BytesIO | bytes,
- *,
- columns: list[int] | list[str] | None = None,
- n_rows: int | None = None,
- use_pyarrow: bool = False,
- memory_map: bool = True,
- storage_options: dict[str, Any] | None = None,
- parallel: ParallelStrategy = 'auto',
- row_count_name: str | None = None,
- row_count_offset: int = 0,
- low_memory: bool = False,
- pyarrow_options: dict[str, Any] | None = None,
- use_statistics: bool = True,
- rechunk: bool = True,
Read into a DataFrame from a parquet file.
- Parameters:
- source
Path to a file, or a file-like object. If the path is a directory, files in that directory will all be read. If
fsspec
is installed, it will be used to open remote files.- columns
Columns to select. Accepts a list of column indices (starting at zero) or a list of column names.
- n_rows
Stop reading from parquet file after reading
n_rows
. Only valid whenuse_pyarrow=False
.- use_pyarrow
Use pyarrow instead of the Rust native parquet reader. The pyarrow reader is more stable.
- memory_map
Memory map underlying file. This will likely increase performance. Only used when
use_pyarrow=True
.- storage_options
Extra options that make sense for
fsspec.open()
or a particular storage connection, e.g. host, port, username, password, etc.- parallel{‘auto’, ‘columns’, ‘row_groups’, ‘none’}
This determines the direction of parallelism. ‘auto’ will try to determine the optimal direction.
- row_count_name
If not None, this will insert a row count column with give name into the DataFrame.
- row_count_offset
Offset to start the row_count column (only use if the name is set).
- low_memory
Reduce memory pressure at the expense of performance.
- pyarrow_options
Keyword arguments for pyarrow.parquet.read_table.
- use_statistics
Use statistics in the parquet to determine if pages can be skipped from reading.
- rechunk
Make sure that all columns are contiguous in memory by aggregating the chunks into a single array.
- Returns:
- DataFrame
See also
Notes
- Partitioned files:
If you have a directory-nested (hive-style) partitioned dataset, you should use the
scan_pyarrow_dataset()
method instead.
- When benchmarking:
This operation defaults to a
rechunk
operation at the end, meaning that all data will be stored continuously in memory. Setrechunk=False
if you are benchmarking the parquet-reader asrechunk
can be an expensive operation that should not contribute to the timings.