Counting non zero values in each column of a dataframe in python

Question

I have a python-pandas-dataframe in which first column is user_id and rest of the columns are tags(tag_0 to tag_122). I have the data in the following format:

Answer 1

Why not use np.count_nonzero?

1. To count the number of non-zeros of an entire dataframe, np.count_nonzero(df)
2. To count the number of non-zeros of all rows np.count_nonzero(df, axis=0)
3. To count the number of non-zeros of all columns np.count_nonzero(df, axis=1)

It works with dates too.