fix crash on unicode level names

[alavrik]

This fixed my problem when calling DataFrame.stack(). Not really familiar with pandas internals, but couldn't find any reason why unicode strings won't be accepted here.

[jreback]

tests would be needed

[alavrik]

To be honest, I don't know pandas internals/tests and I don't use python3. Please consider this as a bug report. Let me know if you need help with reproducing it.

[jreback]

@alavrik

can you show some code which reproduces the error?

the point of a bug report is to say, here is what I did, here's how to reproduce it, its doing x, but I think it should by doing y

we cannot simply change code because it 'looks right'. then what happens when someone decided that some other way looks right?

this is not about knowing pandas internals or not, its about giving a bug report that can lead to tests that can lead to fixed code

sorry for being harsh, but I find lots of people writing code w/o even thinking about testing it.

[alavrik]

@jreback
You are right. Here's the test (Python 2.7.5, Pandas 0.15.2):

import pandas as pd i = pd.MultiIndex( levels=[[u'foo', u'bar'], [u'one', u'two'], [u'a', u'b']], labels=[[0, 0, 1, 1], [0, 1, 0, 1], [1, 0, 1, 0]], names=[u'first', u'second', u'third']) s = pd.Series(0, index=i) s.unstack([1, 2]).stack(0)

and this is the last couple of frames of the error output:

/Users/alavrik/devel/ipython/ve/lib/python2.7/site-packages/pandas/core/index.pyc in sortlevel(self, level, ascending, sort_remaining) 3868 if isinstance(level, (str, int)): 3869 level = [level] -> 3870 level = [self._get_level_number(lev) for lev in level] 3871 3872 # partition labels and shape /Users/alavrik/devel/ipython/ve/lib/python2.7/site-packages/pandas/core/index.pyc in _get_level_number(self, level) 3166 except ValueError: 3167 if not isinstance(level, int): -> 3168 raise KeyError('Level %s not found' % str(level)) 3169 elif level < 0: 3170 level += self.nlevels KeyError: 'Level t not found' 

It is easy to see what's going on. Instead of iterating over [level], it is trying to iterate over the characters of the unicode level name. In this case, it starts with the character t of the level two.

[jreback]

closing in favor of #9856 bug report