python remove all characters from string except characters in list code example

Example 1: remove all occurrences of a character in a list python

>>> x = [1,2,3,2,2,2,3,4]
>>> list(filter(lambda a: a != 2, x))
[1, 3, 3, 4]

Example 2: how to remove all characters from a string in python

s = 'abc12321cba'

print(s.replace('a', ''))