Count the repetition in a column in pandas [duplicate]

Question

I have a column which has the ticketID for a show,(each family member uses the same ticketID ) i want to create a new cloumn which is family size by counting how many times the ticketID is repeated.

ticketID
113796
2543
19950
382653
349211
3101297
PC 17562
113503
113503

Answer 1

try this:

In [123]: df = pd.DataFrame({'ticketID':np.random.randint(0, 3, 5)})

In [124]: df
Out[124]:
   ticketID
0         1
1         2
2         1
3         1
4         2

In [125]: df['family_size'] = df.ticketID.map(df.ticketID.value_counts())

In [126]: df
Out[126]:
   ticketID  family_size
0         1            3
1         2            2
2         1            3
3         1            3
4         2            2

Answer 2

You could use transform

In [152]: df
Out[152]:
   ticketID
0         1
1         2
2         1
3         1
4         2

In [153]: df['family_size'] = df.groupby('ticketID')['ticketID'].transform('size')

In [154]: df
Out[154]:
   ticketID  family_size
0         1            3
1         2            2
2         1            3
3         1            3
4         2            2