BUG: UnicodeEncodeError in test_to_latex_filename (pandas.tests.test_format.TestDataFrameFormatting)

[dhomeier]

Getting this error if (and I think only if) LANG is not defined or not set to any utf8-conforming value on 0.18.0rc1 (Mac OS X 10.10, python 3.4.4, numpy 0.11.0b3):

ERROR: test_to_latex_filename (pandas.tests.test_format.TestDataFrameFormatting)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/tests/test_format.py", line 2614, in test_to_latex_filename
    df.to_latex(path)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/frame.py", line 1593, in to_latex
    encoding=encoding)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/format.py", line 641, in to_latex
    latex_renderer.write_result(f)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/format.py", line 877, in write_result
    buf.write(' & '.join(crow))
UnicodeEncodeError: 'ascii' codec can't encode character '\xdf' in position 7: ordinal not in range(128)

Don't know about the inner workings of this test; if there are any open files involved, this might be relevant: scipy/scipy#5694

[jreback]

hmm I can repro this, but only on mac (usin 3.5 and latest numpy but I don't think numpy matters)

cc @nbonnotte

[jreback]

@dhomeier if you want to experiment on this one. not really sure what the issue is.

[dhomeier]

Seems to me this:
test_format.py:2611

        # test with utf-8 without encoding option
        if compat.PY3:  # python3 default encoding is utf-8

I believe this is not correct; the default encoding is whatever is specified by the LANG (or possibly one of the LC_*) environment variable. If that's not set it falls back to 'ascii'. That's at least what the docs for the builtin open() state:

    In text mode, if encoding is not specified the encoding used is platform
    dependent: locale.getpreferredencoding(False) is called to get the
    current locale encoding.

[nbonnotte]

Uh, I did write that part, but what I meant was "the default for pandas in a python3 environment is utf8", not "the default in python3 is utf8". This was to be consistant with to_csv:

encoding : string, optional
A string representing the encoding to use in the output file, defaults to ‘ascii’ on Python 2 and ‘utf-8’ on Python 3.

It would be interesting to compare to_latex and to_csv, because I don't see any reason why it should work in one case and not in another. I may have missed something, I'll have a look.

[nbonnotte]

Uh, I can't repro this, even though I'm on Mac OS X 10.10, python 3.5.1, numpy 1.10.4, and my LANG is empty.

[dhomeier]

So is the default supposed to be initialised somewhere in the pandas setup independently of the system settings? Otherwise, do you have LC_ALL set? What do you get for this?

>>> import locale
>>> locale.getdefaultlocale()
(None, None)
>>> locale.getpreferredencoding(False)
'US-ASCII'

[jreback]

This gets the pandas encoding.

In [1]: pd.get_option('display.encoding')
Out[1]: 'UTF-8'

I think this is correct in this case, rather its the comparison that's the issue. you need to do like its above

           with codecs.open(path, 'r', encoding='utf-8') as f:
                self.assertEqual(df.to_latex(), f.read())

[nbonnotte]

Hum, I think I did overlook the default behaviour in Python 3 as pointed out by @dhomeier

See this line: the parameter encoding can be None, in which case we go for the default python behavior (which depends on the locale), but both the documentation and the tests expect the default pandas behavior (i.e. UTF-8).

A simple solution could be to replace encoding=None with either 'ascii' or 'utf-8', depending on the version of python being used. Although I don't like much to hardcode it like that way...

[dhomeier]

AFAICS to_csv ultimately gets the default from UnicodeWriter, which sets the default encoding to "utf-8" regardless of the Python version.
I thought to_latex would get it from codecs.open(), which is supposed to use sys.getdefaultencoding().
But this indeed returns 'ascii' in Python 2.7, and 'utf-8' in Python 3, regardless of the environment setting. Just added this check to make sure:

        # test with utf-8 without encoding option
        if compat.PY3:  # python3 default encoding is utf-8
            self.assertEqual(sys.getdefaultencoding(), 'utf-8')
            with tm.ensure_clean('test.tex') as path:
                df.to_latex(path)
                with codecs.open(path, 'r') as f:
                    self.assertEqual(df.to_latex(), f.read())

It's still throwing the error in

            with codecs.open(self.buf, 'w', encoding=encoding) as f:
                latex_renderer.write_result(f)

so maybe the codecs.open() encoding is not passed on to LatexFormatter.write_result(f) (should it?)...

[dhomeier]

@nbonnotte, you could perhaps explicitly call sys.getdefaultencoding() in to_latex() if encoding is None. Though I am wondering now if it makes sense to allow non-ASCII characters in LaTeX output; might still depend on your TeX installation if they are accepted? But for consistency with to_csv one should perhaps use the same as there (or have both resort to sys.getdefaultencoding()).

[nbonnotte]

@dhomeier Of course we want non-ascii characters in LaTeX, they're handled by the inputenc package (or directly by XeLaTeX).

Explicitly calling sys.getdefaultencoding() seems a good idea to me, if that's not what codecs.open looks for implicitly. Can you do a PR?

[dhomeier]

Yes, I may have misread the codecs docstring; for codecs.open it does not explicitly state any default for the encoding. Should we use sys.getdefaultencoding() then or pd.get_option('display.encoding') as put forth by @jreback? And for to_latex only or the same for to_csv? The latter would default to csv.writer with encoding=None, which again would accept unicode characters in Python 3, but not 2; but I don't see any tests for this.