Add number in front of number in columns

Question

I have this example columns

year_short
89
99
97
87
98
00
02
05
10
11
20
22

what I want to do is to make that column into like this

year_long
    1989
    1999
    1997
    1987
    1998
    2000
    2002
    2005
    2010
    2011
    2020
    2022

is it possible to make like that ?

Answer 1

You could use the logic that any two digit year which is less than 25 belongs to the 2000 century, while any value greater than or equal to 25 belongs to the 1900 century:

df["year_long"] = np.where(df["year_short"] < 25, 2000 + df["year_short"], 1900 + df["year_short"])