CODEWITHSUNDEEP
pythonpython-3.xpandas
Chris90
Chris90

Reputation: 1998

Replacing values in column with values from different column if they are a certain value

I have a df below as:

col_a | col_b
Day      Afternoon
Night    NaN
Day      Morning
Lunch    NaN
Day      Morning
Day      Early Morning
Day      Afternoon
Lunch    NaN
Night    NaN

I want to replace all values in col_a that are "Day" with the value they are in col_b but leave all other values as they are in col_a

Thanks

Upvotes: 1

Views: 48

Answers (2)

Carmoreno
Carmoreno

Reputation: 1319

You could use .where method:

df = df.where(df != 'Day', df['col_b'], axis=0)
print(df)

From the documentation:

". . .Where cond is True, keep the original value. Where False, replace with corresponding value from other."

Output mini-example:

    col_a   col_b
0   Afternoon   Afternoon
1   Night   NaN
2   Morning Morning
3   Lunch   Early Morning

Upvotes: 1

wwnde
wwnde

Reputation: 26676

m=df.col_a=='Day'#boolean select
df.loc[m,'col_a']=df.loc[m,'col_b']#mask and replace

Upvotes: 2

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