Find value counts within a pandas dataframe of strings

Question

I want to get the frequency count of strings within a column. One one hand, this is similar to collapsing a dataframe to a set of rows that only reflects the strings in the

Answer 1

Another solution using groupby and value_counts

df.unstack().groupby(level=0).value_counts().unstack().T.fillna(0)
Out[]:
            2017-08-09  2017-08-10
active_1           2.0         3.0
active_1-3         1.0         0.0
active_3-7         1.0         1.0
pre                1.0         1.0

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Or avoiding the last call to fillna

df.unstack().groupby(level=0).value_counts().unstack(fill_value=0).T