how to remove only alphabets from the strings in python code example

Example 1: python remove all except numbers

>>> import re
>>> re.sub('\D', '', 'aas30dsa20')
'3020'

Example 2: python remove letters from string

string = "abc123"
# Method 1
''.join(char for char in string if char.isdigit())

#Method 2
import re
re.sub("[^0-9]", "", string)