`partition_all` fails for sequence of `pd.DataFrame`s

[bnaul]

In [33]: list(partition_all(2, [pd.DataFrame()]))
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-33-f36c7ec14356> in <module>()
----> 1 list(partition_all(2, [pd.DataFrame()]))

~/miniconda3/envs/model/lib/python3.6/site-packages/toolz/itertoolz.py in partition_all(n, seq)
    720         prev = item
    721     if prev[-1] is no_pad:
--> 722         yield prev[:prev.index(no_pad)]
    723     else:
    724         yield prev

~/miniconda3/envs/model/lib/python3.6/site-packages/pandas/core/generic.py in __nonzero__(self)
   1119         raise ValueError("The truth value of a {0} is ambiguous. "
   1120                          "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
-> 1121                          .format(self.__class__.__name__))
   1122
   1123     __bool__ = __nonzero__

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

Works fine when the chunks are all of equal size. Similarly (pd.DataFrame(), 'a').index('a') fails for the same reason. Is there an equivalent way to do this check in itertoolz.py:722 w/o .index()?

[mrocklin]

Hey @bnaul , thanks for the excellent bug report.

Is there an equivalent way to do this check in itertoolz.py:722 w/o .index()?

Probably! But I personally don't know what it is :) Help would be welcome here.