import pandas as pd df = pd.DataFrame(dict(A=[1,1,2,2,3], B=[4,4,5,5,6])) def f(x): return x['A'] < 'taco' df.groupby('A').apply(f) Results in three exceptions stacked on top of each other. See below.

I think it would be great with some basic groupby functionality in numpy, on int's and float's. Using it would be something like a one liner below (just thinking of how a call could look like, not ...