Pandas create new column based on 2 other columns

Asked Sep 07 '21 at 08:16

Active Sep 07 '21 at 08:16

Viewed 11 times

I have DataFrame holds 2 columns. The first one has lower case letter and the other one has True/False values. I'm trying to create third column that changes a lower case letter into an upper case if it marked as True at the second column.

this line won't work for some reason.

df['result_seq'] = df['Letters'].apply(lambda x: x.upper() if df['bool_array'] is True else x)

Thanks!

edited Sep 07 '21 at 08:16

U13-Forward

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asked Sep 07 '21 at 08:16

omer.moses

Use `mask`: `df['Letters'].mask(df['bool_array'], df['Letters'].str.upper())` – mozway Sep 07 '21 at 08:18
It didn't work unfortunately – omer.moses Sep 07 '21 at 08:26
Well, too bad. I guess more details on *how* it did not work could have gotten me to propose an alternative. – mozway Sep 07 '21 at 08:27
It's just the I ran the comment as you showed and all of the letters stayed lower case even if they had True on bool_array at the same row :) – omer.moses Sep 07 '21 at 08:29
Have you assigned the output? `df['result_seq'] = ...` – mozway Sep 07 '21 at 08:31
Ohhh sorry i havn't i though those are inplace changes. It works, very cool. Thanks! – omer.moses Sep 07 '21 at 08:33

Pandas create new column based on 2 other columns

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