Fill DataFrame using np.where with group by conditon

user_15128170 0
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I have a sample df:

id           email1       email2            output
 1       abc@gmail.com    123@gmail.com   random_email1@gmail.com
 1       xyz@gmail.com    234@gmail.com   random_email1@gmail.com
 1            NaN          NaN            random_email1@gmail.com
 2       a123@gmail.com    NaN            random_email2@gmail.com
 2       b123@gmail.com    NaN            random_email2@gmail.com
 2           NaN          lol@gmail.com   random_email2@gmail.com
 3           NaN           NaN            random_email3@gmail.com
 4           NaN          lolz@gmail.com   random_email3@gmail.com

My main goal is to overwrite the output column based on multiple conditions. If email1 has more than one unique email, overwrite all the output with the corresponding IDs with email1_broken. Same goes for email2 but if both have more than one unique email, email2 takes priority and therefore output = email2_broken. Lastly, we retain the email in the current output column if both columns have an id with one unique email.

Attempt:

df['output'] = np.where(df.groupby('id')['email1'].nunique() > 1, 'email1_broken',df['output'])

df['output'] = np.where(df.groupby('id')['email2'].nunique() > 1, 'email2_broken',df['output'])

Desired df:

id           email1       email2            output
 1       abc@gmail.com    123@gmail.com   email2_broken
 1       xyz@gmail.com    234@gmail.com   email2_broken
 1            NaN          NaN            email2_broken
 2       a123@gmail.com    NaN            email1_broken
 2       b123@gmail.com    NaN            email1_broken
 2           NaN          lol@gmail.com   email1_broken
 3           NaN           NaN            random_email3@gmail.com
 4           NaN          lolz@gmail.com  random_email3@gmail.com

Sample data:

import pandas as pd
import numpy as np

cols = ['id','email1','email2', 'output']

data = [
[1   ,  'abc@gmail.com' ,   '123@gmail.com'    , 'random_email1@gmail.com'],
[1   ,  'xyz@gmail.com'  ,  '234@gmail.com'    , 'random_email1@gmail.com'],
[1   ,      np.nan      ,      np.nan          , 'random_email1@gmail.com'],
[2   ,   'a123@gmail.com',     np.nan          , 'random_email2@gmail.com'],
[2   ,   'b123@gmail.com',     np.nan          , 'random_email2@gmail.com'],
[2   ,     np.nan        ,   'lol@gmail.com'   , 'random_email2@gmail.com'],
[3   ,     np.nan        ,     np.nan          , 'random_email3@gmail.com'],
[4   ,     np.nan        ,   'lolz@gmail.com'  , 'random_email3@gmail.com']]

df = pd.DataFrame(data, columns=cols)
pandas dataframe group-by python
2 Answers

You can use np.select (the equivalent of numpy.where when multiple conditions are involved) with transform('nunique'):

g = df.groupby('id')

df['output'] = np.select(
 [g['email2'].transform('nunique').gt(1),
  g['email1'].transform('nunique').gt(1)],
 ['email2_broken', 'email1_broken'],
 df['output'])

print(df)

Output:

  id          email1          email2                   output
0   1   abc@gmail.com   123@gmail.com            email2_broken
1   1   xyz@gmail.com   234@gmail.com            email2_broken
2   1             NaN             NaN            email2_broken
3   2  a123@gmail.com             NaN            email1_broken
4   2  b123@gmail.com             NaN            email1_broken
5   2             NaN   lol@gmail.com            email1_broken
6   3             NaN             NaN  random_email3@gmail.com
7   4             NaN  lolz@gmail.com  random_email3@gmail.com
user_163434640

You are very close:

df['output'] = np.where(df.groupby('id')['email1'].transform('nunique') > 1, 'email1_broken',df['output'])
df['output'] = np.where(df.groupby('id')['email2'].transform('nunique') > 1, 'email2_broken',df['output'])

Use transform to obtain the boolean array with the same shape.

user_147516190
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