.ne fails with abiguous message if comparing a list of columns containing column name 'dtype'

Code Sample, a copy-pastable example if possible

df = pd.DataFrame([[0,1,2,'aa'],[0,1,2,'aa'],[0,1,5,'bb'],[0,1,5,'bb'],[0,1,5,'bb'],['cc',4,4,4]], columns=['a','b','c','dtype'])

df.loc[:, ['a', 'dtype']].ne(df.loc[:, ['a', 'dtype']])

In [10]: df
Out[10]: 
    a  b  c dtype
0   0  1  2    aa
1   0  1  2    aa
2   0  1  5    bb
3   0  1  5    bb
4   0  1  5    bb
5  cc  4  4     4

Problem description

Instead of the expected output, I receive:

In [8]: df.loc[:, ['a','dtype']].ne(df.loc[:, ['a', 'dtype']])
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-8-a0710f18822f> in <module>()
----> 1 df.loc[:, ['a','dtype']].ne(df.loc[:, ['a', 'dtype']])

/home/blistein/env/aan/local/lib/python2.7/site-packages/pandas/core/ops.pyc in f(self, other, axis, level)
   1588                 self, other = self.align(other, 'outer',
   1589                                          level=level, copy=False)
-> 1590             return self._compare_frame(other, na_op, str_rep)
   1591 
   1592         elif isinstance(other, ABCSeries):

/home/blistein/env/aan/local/lib/python2.7/site-packages/pandas/core/frame.pyc in _compare_frame(self, other, func, str_rep)
   4790                 return {col: func(a[col], b[col]) for col in a.columns}
   4791 
-> 4792             new_data = expressions.evaluate(_compare, str_rep, self, other)
   4793             return self._constructor(data=new_data, index=self.index,
   4794                                      columns=self.columns, copy=False)

/home/blistein/env/aan/local/lib/python2.7/site-packages/pandas/core/computation/expressions.pyc in evaluate(op, op_str, a, b, use_numexpr, **eval_kwargs)
    201         """
    202 
--> 203     use_numexpr = use_numexpr and _bool_arith_check(op_str, a, b)
    204     if use_numexpr:
    205         return _evaluate(op, op_str, a, b, **eval_kwargs)

/home/blistein/env/aan/local/lib/python2.7/site-packages/pandas/core/computation/expressions.pyc in _bool_arith_check(op_str, a, b, not_allowed, unsupported)
    173         unsupported = {'+': '|', '*': '&', '-': '^'}
    174 
--> 175     if _has_bool_dtype(a) and _has_bool_dtype(b):
    176         if op_str in unsupported:
    177             warnings.warn("evaluating in Python space because the {op!r} "

/home/blistein/env/aan/local/lib/python2.7/site-packages/pandas/core/generic.pyc in __nonzero__(self)
   1574         raise ValueError("The truth value of a {0} is ambiguous. "
   1575                          "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
-> 1576                          .format(self.__class__.__name__))
   1577 
   1578     __bool__ = __nonzero__

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Expected Output

       a      c
0  False  False
1  False  False
2  False  False
3  False  False
4  False  False
5  False  False

Alternative: a descriptive Error Message, telling me I can’t use ‘dtype’ as column name.

Output of pd.show_versions()

[paste the output of pd.show_versions() here below this line] INSTALLED VERSIONS

commit: None python: 2.7.12.final.0 python-bits: 64 OS: Linux OS-release: 4.15.0-29-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: en_US.utf8 LANG: en_US.UTF-8 LOCALE: None.None

pandas: 0.23.4 pytest: 2.8.7 pip: 18.0 setuptools: 40.0.0 Cython: None numpy: 1.11.0 scipy: 0.17.0 pyarrow: None xarray: None IPython: 5.5.0 sphinx: None patsy: 0.4.1 dateutil: 2.7.3 pytz: 2014.10 blosc: None bottleneck: None tables: 3.2.2 numexpr: 2.4.3 feather: None matplotlib: 1.5.1 openpyxl: 2.3.0 xlrd: 0.9.4 xlwt: 0.7.5 xlsxwriter: None lxml: 3.5.0 bs4: None html5lib: 1.0.1 sqlalchemy: None pymysql: 0.7.2.None psycopg2: 2.6.1 (dt dec mx pq3 ext lo64) jinja2: 2.10 s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: None

[TomAugspurger]

Maybe pandas/tests/test_expressions.py

[baidoosik]

@TomAugspurger hi, i fix _has_bool_dtype function. but i don’t know which test directory is right directory. this is my first try to contribute open source…could you tell me which directory is more appropriate? thank you.