BUG A file-like object as arg to df.to_csv must have the method getvalue #259
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We need a file-like object with the `getvalue` method (yes for StringIO, no for TextIOWrapper). Otherwise when passing a file-like obj to pandas v0.23.1 df.to_csv, the lack of the getvalue method raises an error.
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AppVeyor has been turned on, but obviously there's no AppVeyor configuration yet (upcoming from #258) and hence the relevant build "failure", which should be ignored for this PR. |
| @@ -173,7 +173,7 @@ def test_stash_local_data_from_dataframe_csv(mock_file): | |||
| assert _model._stash_dataframe_as_csv(df, mock.Mock()) == -11 | |||
| mock_file.assert_called_once_with(mock.ANY, name='modelpipeline_data.csv', | |||
| client=mock.ANY) | |||
| assert isinstance(mock_file.call_args[0][0], BytesIO) | |||
| assert isinstance(mock_file.call_args[0][0], StringIO) | |||
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Shouldn't this fail in the Python27 tests? That is, won't this be a BytesIO object for Python27?
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Good question! Behold --
Python 2.7, six 1.11.0:
In [2]: from six import StringIO, BytesIO
In [3]: s = StringIO()
In [4]: b = BytesIO()
In [5]: isinstance(s, StringIO)
Out[5]: True
In [6]: isinstance(s, BytesIO)
Out[6]: True
In [7]: isinstance(b, StringIO) # This is why we didn't get the expected failure?
Out[7]: True
In [8]: isinstance(b, BytesIO)
Out[8]: TruePython 3.6, six 1.11.0 (where everything makes sense to me):
In [1]: from six import StringIO, BytesIO
In [2]: s = StringIO()
In [3]: b = BytesIO()
In [4]: isinstance(s, StringIO)
Out[4]: True
In [5]: isinstance(s, BytesIO)
Out[5]: False
In [6]: isinstance(b, StringIO)
Out[6]: False
In [7]: isinstance(b, BytesIO)
Out[7]: TrueThere was a problem hiding this comment.
Huh. Thanks for looking into that.
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I think the test passes because of https://github.com/benjaminp/six/blob/1.11.0/six.py#L664 . Given that equality, do we need the if six.PY3 conditional?
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Good point! Although I don't have a problem merging as is, either.
Since
pandasv0.23.1 (specifically from pandas-dev/pandas#21300), if a file-like object is passed intodf.to_csv, the object must have the methodgetvalue, or else anAttributeErroris raised (which is what we have observed from #258). Anio.TextIOWrapperobject doesn't have the methodgetvalue, which caused the latest build failures in #258. This PR switches toio.StringIOinstead.