Adding a 'count' column to the result of a groupby in pandas?

Question

I think this is a fairly basic question, but I can\'t seem to find the solution.

I have a pandas dataframe similar to the following:

import pandas as         


        

Answer 1

pandas >= 1.1: DataFrame.value_counts

This is an identical replacement for df.groupby(['A', 'B']).size().

df.value_counts(['A', 'B'])

A  B
z  r    2
x  p    2
y  q    1
dtype: int64

df.value_counts(['A', 'B']).reset_index(name='c')

   A  B  c
0  z  r  2
1  x  p  2
2  y  q  1