Pandas: read_csv fails to read file if there are cyrillic symbols in filename

[c-fos]

Code Sample, a copy-pastable example if possible

import pandas
cyrillic_filename = "./файл_1.csv"
# 'c' engine fails:
df = pandas.read_csv(cyrillic_filename, engine="c", encoding="cp1251")
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-18-9cb08141730c> in <module>()
      2 
      3 cyrillic_filename = "./файл_1.csv"
----> 4 df = pandas.read_csv(cyrillic_filename , engine="c", encoding="cp1251")

d:\0_dev\services\protocol_sort\venv\lib\site-packages\pandas\io\parsers.py in parser_f(filepath_or_buffer, sep, delimiter, header, names, index_col, usecols, squeeze, prefix, mangle_dupe_cols, dtype, engine, converters, true_values, false_values, skipinitialspace, skiprows, nrows, na_values, keep_default_na, na_filter, verbose, skip_blank_lines, parse_dates, infer_datetime_format, keep_date_col, date_parser, dayfirst, iterator, chunksize, compression, thousands, decimal, lineterminator, quotechar, quoting, escapechar, comment, encoding, dialect, tupleize_cols, error_bad_lines, warn_bad_lines, skipfooter, skip_footer, doublequote, delim_whitespace, as_recarray, compact_ints, use_unsigned, low_memory, buffer_lines, memory_map, float_precision)
    653                     skip_blank_lines=skip_blank_lines)
    654 
--> 655         return _read(filepath_or_buffer, kwds)
    656 
    657     parser_f.__name__ = name

d:\0_dev\services\protocol_sort\venv\lib\site-packages\pandas\io\parsers.py in _read(filepath_or_buffer, kwds)
    403 
    404     # Create the parser.
--> 405     parser = TextFileReader(filepath_or_buffer, **kwds)
    406 
    407     if chunksize or iterator:

d:\0_dev\services\protocol_sort\venv\lib\site-packages\pandas\io\parsers.py in __init__(self, f, engine, **kwds)
    762             self.options['has_index_names'] = kwds['has_index_names']
    763 
--> 764         self._make_engine(self.engine)
    765 
    766     def close(self):

d:\0_dev\services\protocol_sort\venv\lib\site-packages\pandas\io\parsers.py in _make_engine(self, engine)
    983     def _make_engine(self, engine='c'):
    984         if engine == 'c':
--> 985             self._engine = CParserWrapper(self.f, **self.options)
    986         else:
    987             if engine == 'python':

d:\0_dev\services\protocol_sort\venv\lib\site-packages\pandas\io\parsers.py in __init__(self, src, **kwds)
   1603         kwds['allow_leading_cols'] = self.index_col is not False
   1604 
-> 1605         self._reader = parsers.TextReader(src, **kwds)
   1606 
   1607         # XXX
pandas\_libs\parsers.pyx in pandas._libs.parsers.TextReader.__cinit__ (pandas\_libs\parsers.c:4209)()
pandas\_libs\parsers.pyx in pandas._libs.parsers.TextReader._setup_parser_source (pandas\_libs\parsers.c:8895)()
OSError: Initializing from file failed

# 'python' engine work:
df = pandas.read_csv(cyrillic_filename, engine="python", encoding="cp1251")
df.size
>>172440

# 'c' engine works if filename can be encoded to utf-8
latin_filename = "./file_1.csv"
df = pandas.read_csv(latin_filename, engine="c", encoding="cp1251")
df.size
>>172440

Problem description

The 'c' engine should read the files with non-UTF-8 filenames

Expected Output

File content readed into dataframe

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.6.1.final.0
python-bits: 32
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 42 Stepping 7, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.20.3
pytest: None
pip: 9.0.1
setuptools: 28.8.0
Cython: None
numpy: 1.13.2
scipy: 0.19.1
xarray: None
IPython: 6.2.1
sphinx: None
patsy: None
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: 2.4.8
xlrd: None
xlwt: None
xlsxwriter: None
lxml: 4.0.0
bs4: None
html5lib: 1.0b10
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None
None

[gfyoung]

@c-fos : Thanks for reporting this! A couple of questions:

• If you change the engine to Python, does it make a difference?
• Can you open the file simply by calling open(filename)?

I'm trying to figure out if this is just a general Python issue of not handling Cyrillic characters well OR if this a pandas-specific issue.

[c-fos]

cyrillic_filename = "./файл_1.csv"

# 'python' engine is working:
df = pandas.read_csv(cyrillic_filename, engine="python", encoding="cp1251")
df.size
>>172440

# simple open in working
fd = open(cyrillic_filename)
fd
>><_io.TextIOWrapper name='./файл_1.csv' mode='r' encoding='cp1251'>

[gfyoung]

Alright, this is indeed a pandas-specific issue with the C engine. More than welcome to track this down and submit a patch for it!

[gfyoung]

The error is raised here:

https://github.com/pandas-dev/pandas/blob/def3bce010eb0eaea2580ad6b6f44c0318314296/pandas/_libs/parsers.pyx#L709-L718

The culprit function I believe is here:

https://github.com/pandas-dev/pandas/blob/def3bce010eb0eaea2580ad6b6f44c0318314296/pandas/_libs/src/parser/io.c#L24-L49

What worries me is that it might have to do with the open function, in which case we might have hit a dead end (and perhaps it would no longer be a pandas-issue).

[jreback]

duplicate of https://github.com/pandas-dev/pandas/issues/15086, there was a PR to fix this #15092 but it was erased somehow. This was a change in default file encoding on 3.6 on windows. There is a PEP reference in there. To solve we just treat the filename as bytes and decode as utf8. Welcome to have a patch.

[fanguoguo]

File "pandas/_libs/parsers.pyx", line 384, in pandas._libs.parsers.TextReader.__cinit__
File "pandas/_libs/parsers.pyx", line 695, in pandas._libs.parsers.TextReader._setup_parser_source

[fingoldo]

I can not believe this. It's year 2019 now, pandas v 23.4 and this issue with Cyrillic paths and C engine is STILL NOT FIXED, even after so many issue reports and questions on stackoverflow. Open source community seems to be no better than Microsoft in this regard, where known bugs are not getting fixed for years.

[gfyoung]

Open source community seems to be no better than Microsoft in this regard, where known bugs are not getting fixed for years.

@fingoldo : Sorry about this! We do get a lot of issues every day, and unlike at Microsoft, we have way fewer code maintainers to work and address all of these issues that we receive.

That being said, if you would like to tackle the issue, that would be great! Part of the issue that we have right now is that it's hard for us to test and validate any fixes, so a community contribution would be most welcome for something like this.

xref https://github.com/pandas-dev/pandas/issues/15086#issuecomment-445799283

[fingoldo]

@gfyoung sorry for the harsh words and thank you for your kind reply, I personally don't know how to fix that issue but please, if someone from devs who has actually created relevant modules sees this thread, roll out the fix, it's really embarassing to still have that error when engine is set to C...

[gfyoung]

it's really embarassing to still have that error when engine is set to C

@fingoldo : Yeah, it's awkward no doubt, but I hope you understand that there are many of these types of "embarrassing errors" than there are man-hours (devs and contributors combined) to correct them, especially if people have a hard time reproducing them.

Lucky for you, I currently have in my possession a Windows machine, and I was able to patch this issue pretty quickly in a PR:

https://github.com/pandas-dev/pandas/pull/24758

[fingoldo]

Amazing thank you so much!!!