In pandas, can I compare 2 columns where first column has instance id and email address in second. E-CodePudding

Have this table where an email address (col 1) can be associated with multiple instances (col 2). For instance, [email protected] is linked to instance id 158 and 274.

In pandas, how do I look up how many instances / which instances are associated with a particular email address.

CodePudding user response：

Try this

import pandas  as pd
import numpy as np

df = pd.read_csv('./data/mails.csv')
df

     email address  instance ID
0    [email protected]          158
1    [email protected]          189
2    [email protected]          274
3     [email protected]          274
4     [email protected]          274
5   [email protected]          274
6  [email protected]          274
7    [email protected]          200

# count instances by mail
print(df.groupby(by='email address').count())

                 instance ID
email address               
[email protected]               1
[email protected]              2
[email protected]             1
[email protected]            1
[email protected]               1
[email protected]              2

# instances by mail
df.pivot_table(index=['email address', 'instance ID'])