[FIXED] Alternatives to update rows

Issue

I have the following sample data:

	date	value
0	2021/05	50
1	2021/06	60
2	2021/07	70
3	2021/08	80
4	2021/09	90
5	2021/10	100

I want to update the data in the 'date' column, where for example '2021/05' becomes '05/10/2021', '2021/06' becomes '06/12/2021' and so long (I have to choose the new date manually for every row).

Is there a better/more clever way to do it instead of:

for i in df.index:
    if df['date'][i] == '2021/05':
        df['date'][i] = '05/10/2021'
    elif df['date'][i] == '2021/06':
        df['date'][i] = '06/12/2021'

The problem is that there are more than hundred rows that have to be updated and the code above will be tremendously long.

Solution

We can use the select method from numpy like so :

import numpy as np


condlist = [df['date'] == '2021/05', 
            df['date'] == '2021/06']

choicelist = ['05/10/2021',
              '06/12/2021']            

df['date'] = np.select(condlist, choicelist, default=np.nan)

Answered By - tlentali