Python pandas: Add a column to my dataframe that counts a variable

Question

I have a dataframe \'gt\' like this:

org     group
org1      1
org2      1
org3      2
org4      3
org5      3
org6      3

and I would like to

Answer 1

Call transform this will return a Series aligned with the original df:

In [223]:

df['count'] = df.groupby('group')['group'].transform('count')
df
Out[223]:
    org  group  count
0  org1      1      2
1  org2      1      2
2  org3      2      1
3  org4      3      3
4  org5      3      3
5  org6      3      3