How to apply lambda function to specific column based on the values in the adjacent column-CodePudding

I am trying a apply a lambda function to a pandas data frame. My question is how can I apply a lambda function to column a based on value in column b using if statement.

df['B'].apply(lambda x: x 3 if x<(#the value in column C) else x)

CodePudding user response：

You need to call apply on the dataframe, with axis=1, instead of on the B column:

>>> df.apply(lambda x: x['B'] 3 if x['B']<x['C'] else x['B'], axis=1)
0     8
1     8
2    10
dtype: int64

But, a much more efficient (faster) way would be to do this:

>>> df['B']   df['B'].lt(df['C']) * 3
0     8
1     8
2    10
dtype: int64