BinGrouper breaks on DataFrame.transform (original) (raw)

import pandas as pd import numpy as np from pandas.tseries.resample import TimeGrouper import pandas.util.testing as tm

df = tm.makeTimeDataFrame() tg = TimeGrouper('M')

func = lambda x: (x - 1) df.groupby(tg).transform(func)

/externals/pandas/pandas/core/groupby.py in _get_compressed_labels(self)
   1360     def _get_compressed_labels(self):
-> 1361         all_labels = [ping.labels for ping in self.groupings]
   1362         if self._overflow_possible:

TypeError: 'NoneType' object is not iterable

Seems related to #8049 as that check group_info which errors on BinGrouper since there are no groupings