how to replace alphabetic values to another column pandas python

I got the following df

How can i get the following df

I filtered the alphabetic values from it with replace function. And then using the update function but its not working. Does someone know a better way

housenumber = df['huisnummer'].str.replace('[^a-zA-Z.,-/]', '')

df.set_index('serial', inplace=True)
df.update(huisnummer)
df.reset_index(inplace=True)  # to recover the initial structure

>Solution :

Use .str.extract:

df['housenumber_extra'] = df['housenumber'].str.extract(r'\d+([^\d].+)$')[0].str.strip().fillna(df['housenumber_extra']).str.upper()

Output:

>>> df
  housenumber housenumber_extra
0           1               NaN
1           2                 A
2         55a                 A
3        55-4                -4
4      3455 C                 C