How to replace last 4 digits in Pandas Dataframe by 0101 if they are 9999 (Python)

I have a Dataframe that looks like this:

OrdNo  year
1     20059999
2     20070830
3     20070719
4     20030719
5     20039999
6     20070911
7     20050918
8     20070816
9     20069999

How to replace last 4 digits in the Pandas Dataframe by 0101 if they are 9999?

Thanks

>Solution :

Assuming your year column is of type str:

df["year"] = df["year"].str.replace("(9999)$", "0101")

If it is of numeric type

df["year"] = pd.to_numeric(df["year"].astype(str).str.replace("(9999)$", "0101"), errors="coerce")