CODEWITHSUNDEEP
python-3.xpandasdataframe
Rolando
Rolando

Reputation: 62596

How to modify original dataframe after updating its value off of a filtered view/subset of rows from the original dataframe?

I have a pandas dataframe "df" that contains:

SPORT, NAME, TEST 
Tennis, A, TESTA
Tennis, B, TESTB
Basketball, C, TESTC
Volleyball, D, TESTC

I want to change the 'TEST' column only for the ones where SPORT == 'Tennis' to 'CHANGED'. I tried the following:

tennislist = df[df['SPORT'] == 'Tennis']
tennislist['TEST'] = 'CHANGED'

While tennislist appears to be updated with the correct values, when I then print out the original "df", I see no changes at all. How can I make it so that even though I filtered on tennislist to update the column 'TEST' that those changes also updates the original "df" that I filtered from?

Upvotes: 1

Views: 1024

Answers (1)

RichieV
RichieV

Reputation: 5183

You can modify the values in df with

df.loc[df['SPORT'].eq('Tennis'), 'TEST'] = 'CHANGED'

Your code is currently creating a new object called tennislist which is a subset of the rows in df, but if you change tennislist it will not be reflected in df.

Upvotes: 1

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