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Add ZIP file decompression and TestCompression. #12175

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.18.1.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@ Partial string indexing now matches on ``DateTimeIndex`` when part of a ``MultiI
Other Enhancements
^^^^^^^^^^^^^^^^^^

- ``pd.read_csv()`` now supports opening ZIP files that contains a single CSV (:issue:`12175`)
- ``pd.read_msgpack()`` now always gives writeable ndarrays even when compression is used (:issue:`12359`).

.. _whatsnew_0181.api:
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15 changes: 15 additions & 0 deletions pandas/io/common.py
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Expand Up @@ -360,6 +360,21 @@ def _get_handle(path, mode, encoding=None, compression=None):
elif compression == 'bz2':
import bz2
f = bz2.BZ2File(path, mode)
elif compression == 'zip':
import zipfile
zip_file = zipfile.ZipFile(path)
zip_names = zip_file.namelist()

if len(zip_names) == 1:
file_name = zip_names.pop()
f = zip_file.open(file_name)
elif len(zip_names) == 0:
raise ValueError('Zero files found in ZIP file {}'
.format(path))
else:
raise ValueError('Multiple files found in ZIP file.'
' Only one file per ZIP :{}'
.format(zip_names))
else:
raise ValueError('Unrecognized compression type: %s' %
compression)
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32 changes: 27 additions & 5 deletions pandas/io/parsers.py
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Expand Up @@ -158,11 +158,12 @@ class ParserWarning(Warning):
information
<http://pandas.pydata.org/pandas-docs/stable/io.html#io-chunking>`_ on
``iterator`` and ``chunksize``.
compression : {'infer', 'gzip', 'bz2', None}, default 'infer'
For on-the-fly decompression of on-disk data. If 'infer', then use gzip or
bz2 if filepath_or_buffer is a string ending in '.gz' or '.bz2',
respectively, and no decompression otherwise. Set to None for no
decompression.
compression : {'gzip', 'bz2', 'zip', 'infer', None}, default 'infer'
For on-the-fly decompression of on-disk data. If 'infer', then use gzip,
bz2 or zip if filepath_or_buffer is a string ending in '.gz', '.bz2' or
'.zip', respectively, and no decompression otherwise. New in 0.18.1: ZIP
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need a versionadded tag here

compression If using 'zip', the ZIP file must contain only one data file
to be read in. Set to None for no decompression.
thousands : str, default None
Thousands separator
decimal : str, default '.'
Expand Down Expand Up @@ -273,6 +274,8 @@ def _read(filepath_or_buffer, kwds):
inferred_compression = 'gzip'
elif filepath_or_buffer.endswith('.bz2'):
inferred_compression = 'bz2'
elif filepath_or_buffer.endswith('.zip'):
inferred_compression = 'zip'
else:
inferred_compression = None
else:
Expand Down Expand Up @@ -1397,6 +1400,25 @@ def _wrap_compressed(f, compression, encoding=None):
data = bz2.decompress(f.read())
f = StringIO(data)
return f
elif compression == 'zip':
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this seems quite duplicative (I know it was there before). any way you can simply use _get_handle? (which already has this embeded)

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This is not that trivial. wrap_compressed() handles file objects. I'd have to refactor this code to handle for this. See the logic below

        if isinstance(f, compat.string_types):
            f = _get_handle(f, 'r', encoding=self.encoding,
                            compression=self.compression)
        elif self.compression:
            f = _wrap_compressed(f, self.compression, self.encoding)

I would then have to modify _get_handle to deal with file objects as well as strings

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ok then is possible to isolate this so each is just a function call to a common function? (just trying to avoid this code duplication)

import zipfile
zip_file = zipfile.ZipFile(f)
zip_names = zip_file.namelist()
print('ZIPNAMES' + zip_names)

if len(zip_names) == 1:
file_name = zip_names.pop()
f = zip_file.open(file_name)
return f

elif len(zip_names) == 0:
raise ValueError('Corrupted or zero files found in compressed '
'zip file %s', zip_file.filename)

else:
raise ValueError('Multiple files found in compressed '
'zip file %s', str(zip_names))

else:
raise ValueError('do not recognize compression method %s'
% compression)
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