Multiple condition in pandas dataframe - np.where

Question

I have the following dataframe

Year          M  
1991-1990     10
1992-1993      9

What I am trying to so is a if statement: =IF(M>9,LEFT(Year),RIGHT(C2,4))*1

So basically if M if 10 choose the left value of the column year else choose the second value

I tried using np.where but I have no idea how to choose between two values in the same column.

Help?

Answer 1

You can do this:

In [448]:  df['val'] = np.where( df['M'].gt(9),\ 
     ...:                       df.Year.str.split('-').tolist()[0],\ 
     ...:                       df.Year.str.split('-').tolist()[1] )                                                                                                                                         


In [444]: df                                                                                                                                                                                                
Out[444]: 
        Year   M   val
0  1991-1990  10  1991
1  1992-1993   9  1993