Replace all specific values in dataframe with value in another column-CodePudding

I have a dataframe where I want to replace all values of 999999 with another column value, while leaving all other values alone. Here is an example of what I have now:

Account	max val	Biology	Statistics
Bill	100	999999	200
Frank	150	150	999999
Wendy	90	999999	100

Here is what I want the dataframe to look like:

Account	max val	Biology	Statistics
Bill	100	100	200
Frank	150	150	150
Wendy	90	90	100

Is there an efficient way to accomplish this?

Thanks in advance.

CodePudding user response：

I will do

df = df.mask(df==999999).ffill(axis = 1)
  Account max val Biology Statistics
0    Bill     100     100      200.0
1   Frank     150   150.0      150.0
2   Wendy      90      90      100.0