df.group by column count value code example
Example 1: pandas groupby count as new column
In [12]: df.groupby(["item", "color"])["id"].count().reset_index(name="count")
Out[12]:
item color count
0 car black 2
1 truck blue 1
2 truck red 2
Example 2: pandas groupby counts
df[['col1', 'col2', 'col3', 'col4']].groupby(['col1', 'col2']).agg(['mean', 'count'])