112 lines
3.3 KiB
Python
112 lines
3.3 KiB
Python
""" feather-format compat """
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from distutils.version import LooseVersion
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from pandas import DataFrame, RangeIndex, Int64Index
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from pandas.compat import range
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from pandas.io.common import _stringify_path
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def _try_import():
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# since pandas is a dependency of feather
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# we need to import on first use
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try:
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import feather
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except ImportError:
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# give a nice error message
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raise ImportError("the feather-format library is not installed\n"
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"you can install via conda\n"
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"conda install feather-format -c conda-forge\n"
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"or via pip\n"
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"pip install -U feather-format\n")
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try:
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LooseVersion(feather.__version__) >= LooseVersion('0.3.1')
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except AttributeError:
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raise ImportError("the feather-format library must be >= "
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"version 0.3.1\n"
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"you can install via conda\n"
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"conda install feather-format -c conda-forge"
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"or via pip\n"
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"pip install -U feather-format\n")
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return feather
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def to_feather(df, path):
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"""
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Write a DataFrame to the feather-format
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Parameters
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----------
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df : DataFrame
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path : string file path, or file-like object
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"""
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path = _stringify_path(path)
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if not isinstance(df, DataFrame):
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raise ValueError("feather only support IO with DataFrames")
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feather = _try_import()
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valid_types = {'string', 'unicode'}
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# validate index
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# --------------
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# validate that we have only a default index
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# raise on anything else as we don't serialize the index
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if not isinstance(df.index, Int64Index):
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raise ValueError("feather does not support serializing {} "
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"for the index; you can .reset_index()"
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"to make the index into column(s)".format(
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type(df.index)))
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if not df.index.equals(RangeIndex.from_range(range(len(df)))):
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raise ValueError("feather does not support serializing a "
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"non-default index for the index; you "
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"can .reset_index() to make the index "
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"into column(s)")
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if df.index.name is not None:
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raise ValueError("feather does not serialize index meta-data on a "
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"default index")
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# validate columns
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# ----------------
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# must have value column names (strings only)
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if df.columns.inferred_type not in valid_types:
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raise ValueError("feather must have string column names")
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feather.write_dataframe(df, path)
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def read_feather(path, nthreads=1):
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"""
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Load a feather-format object from the file path
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.. versionadded 0.20.0
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Parameters
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----------
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path : string file path, or file-like object
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nthreads : int, default 1
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Number of CPU threads to use when reading to pandas.DataFrame
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.. versionadded 0.21.0
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Returns
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-------
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type of object stored in file
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"""
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feather = _try_import()
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path = _stringify_path(path)
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if LooseVersion(feather.__version__) < LooseVersion('0.4.0'):
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return feather.read_dataframe(path)
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return feather.read_dataframe(path, nthreads=nthreads)
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