0.16.1 No columns to parse from file

[shadow-identity]

I've updated Pandas from 0.14.1 (all was good) to 0.16.1 and now I have that exception:

Error
Traceback (most recent call last):
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/tests/test_reports.py", line 618, in test_no_reports
    response = self.request(request)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/tests/test_common.py", line 56, in request
    HTTP_COOKIE={})
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/test/client.py", line 479, in post
    secure=secure, **extra)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/test/client.py", line 294, in post
    secure=secure, **extra)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/test/client.py", line 355, in generic
    return self.request(**r)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/test/client.py", line 437, in request
    six.reraise(*exc_info)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/core/handlers/base.py", line 111, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/views.py", line 160, in dispatch
    result = self.view(request)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/views.py", line 236, in view
    return getattr(handler, action)(**args)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/utils.py", line 74, in inner
    result = func(*args, **kwargs)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/utils.py", line 102, in inner
    return func(*args, **kwargs)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/utils.py", line 120, in inner
    return F(*args, **kwargs)
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/utils.py", line 902, in get_stat
    self._get_pandas_dataframe()
  File "/home/nedr/progs/MEA-FormBuilder/formbuilder_core/utils.py", line 881, in _get_pandas_dataframe
    self.data = pandas.read_csv(cStringIO.StringIO(self.report.body))
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/pandas/io/parsers.py", line 474, in parser_f
    return _read(filepath_or_buffer, kwds)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/pandas/io/parsers.py", line 250, in _read
    parser = TextFileReader(filepath_or_buffer, **kwds)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/pandas/io/parsers.py", line 566, in __init__
    self._make_engine(self.engine)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/pandas/io/parsers.py", line 705, in _make_engine
    self._engine = CParserWrapper(self.f, **self.options)
  File "/home/nedr/progs/env/mea-formbuilder/lib/python2.7/site-packages/pandas/io/parsers.py", line 1072, in __init__
    self._reader = _parser.TextReader(src, **kwds)
  File "pandas/parser.pyx", line 512, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:4814)
ValueError: No columns to parse from file

[jorisvandenbossche]

@shadow-identity You will have to provide some more details ..

E.g. provide some example data that reproduces the error. How does cStringIO.StringIO(self.report.body) look like?

[shadow-identity]

@jorisvandenbossche self.report.body is just a blank string ('')
cStringIO.StringIO returns file-like object from string
So exception raises only when file is blank. In other cases (self.report.body contains csv) all works fine.
It is unexpected for me because with 0.14.1 exception not raises.

[jreback]

This raises in 0.14.1 as well. CParserError: Passed header=0 but only 0 lines in file. So this is correct.

[shadow-identity]

@jorisvandenbossche I'm using this code:

        try:
            self.data = pandas.read_csv(cStringIO.StringIO(self.report.body))
        except CParserError as e:
            raise formbuilder_core.views.ValidationException('report', 'insufficient')

And I need to just install 0.14.1 back to disappear exception I've reported...

[jorisvandenbossche]

Ah, so it seems the exception type has changed from CParseError to ValueError. So you can probably catch both to have the code work for both pandas versions

[szeitlin]

Yeah I'm noticing something similar, but even more strange. If I try to read the file and it fails, once that exception is raised, I can't get it to work even with the correct parameters. However, if I independently read the file with the correct parameters, it does work. It's like it won't let go of the exception once it's raised (?). e.g. this works, so I know there's nothing wrong with my file:

pd.read_csv('myfile.csv', header=4)

but this doesn't work:

     try:
         one = pd.read_csv(csvfile)
     except CParserError as e:                          #it is catching the error
         two = pd.read_csv(csvfile, header=4)         #this fails

But it used to work with very similar code (in version 15.1):

        try:
           df = pd.read_csv(fullpath)
           print("successfully read file named " + filename)
       except pd.parser.CParserError as e:
           print("parser error, I'll try again")
           try:
               df = pd.read_csv(fullpath, skiprows=4)
               print("successfully read file named " + filename)
           except Exception as e:
               raise FileTypeUnknownError
               print(type(e))

(note that I also tried to catch it as a ValueError, but it still fails with "No columns to parse from file")