/
feather_format.py
103 lines (75 loc) · 2.92 KB
/
feather_format.py
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""" feather-format compat """
from pandas.compat._optional import import_optional_dependency
from pandas import DataFrame, Int64Index, RangeIndex
from pandas.io.common import stringify_path
def to_feather(df: DataFrame, path):
"""
Write a DataFrame to the feather-format
Parameters
----------
df : DataFrame
path : string file path, or file-like object
"""
import_optional_dependency("pyarrow")
from pyarrow import feather
path = stringify_path(path)
if not isinstance(df, DataFrame):
raise ValueError("feather only support IO with DataFrames")
valid_types = {"string", "unicode"}
# validate index
# --------------
# validate that we have only a default index
# raise on anything else as we don't serialize the index
if not isinstance(df.index, Int64Index):
typ = type(df.index)
raise ValueError(
f"feather does not support serializing {typ} "
"for the index; you can .reset_index() "
"to make the index into column(s)"
)
if not df.index.equals(RangeIndex.from_range(range(len(df)))):
raise ValueError(
"feather does not support serializing a "
"non-default index for the index; you "
"can .reset_index() to make the index "
"into column(s)"
)
if df.index.name is not None:
raise ValueError(
"feather does not serialize index meta-data on a default index"
)
# validate columns
# ----------------
# must have value column names (strings only)
if df.columns.inferred_type not in valid_types:
raise ValueError("feather must have string column names")
feather.write_feather(df, path)
def read_feather(path, columns=None, use_threads: bool = True):
"""
Load a feather-format object from the file path.
Parameters
----------
path : str, path object or file-like object
Any valid string path is acceptable. The string could be a URL. Valid
URL schemes include http, ftp, s3, and file. For file URLs, a host is
expected. A local file could be:
``file://localhost/path/to/table.feather``.
If you want to pass in a path object, pandas accepts any
``os.PathLike``.
By file-like object, we refer to objects with a ``read()`` method,
such as a file handler (e.g. via builtin ``open`` function)
or ``StringIO``.
columns : sequence, default None
If not provided, all columns are read.
.. versionadded:: 0.24.0
use_threads : bool, default True
Whether to parallelize reading using multiple threads.
.. versionadded:: 0.24.0
Returns
-------
type of object stored in file
"""
import_optional_dependency("pyarrow")
from pyarrow import feather
path = stringify_path(path)
return feather.read_feather(path, columns=columns, use_threads=bool(use_threads))