pydata/pandas — comment on commit 2246fb32d6c72b5df796af77b50229302aceaa95
File: pandas/core/groupby.py line 939
By adamklein:

Good point, much better not to. Reason is:

/home/adam/code/pandas/pandas/core/groupby.py(1071)aggregate()
1069 ret = self._aggregate_multiple_funcs(func_or_funcs)
1070 else:
-> 1071 if len(self.grouper.groupings) > 1:

Should probably change to self.grouper.ngroups