pandas groupby and boolean selection

Question

I often end up doing things like this in pandas:

s2 = s1.groupby(level=1).sum()
s2 = s2[s2>25]

In words, I do some groupby operation and then want to keep only results that meet some condition for the result.

Is there a way to do with in one line? More specifically, is it possible to do this without creating the series and then doing the Boolean selection in a second step?

Answer 1

Assuming s1 is a pandas.Series

1. You can pass level to pd.Series.sum
2. pd.Series.compress is handy

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s2.sum(level=1).compress(lambda s: s.gt(25))

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Assuming s1 is a pandas.DataFrame
And that there is a column names 'col'

s.sum(level=1).query('col > 25')