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

I do not know why I addict to using apply in this strange way ...

df.apply(lambda x : x.groupby(x).count()).fillna(0)
Out[31]: 
            2017-08-09  2017-08-10
active_1             2         3.0
active_1-3           1         0.0
active_3-7           1         1.0
pre                  1         1.0

Or

import collections
df.apply(lambda x : pd.Series(collections.Counter(x))).fillna(0)

As what I expected simple for loop is faster than apply

pd.concat([pd.Series(collections.Counter(df[x])) for x in df.columns],axis=1)