python regex check if string matches code example

Example 1: check string equal with regular expression python

import re
pattern = re.compile("^([A-Z][0-9]+)+$")
pattern.match(string)

Example 2: check if valid regex string python

import re
string = '['
try:
    re.compile(string)
    is_valid = True
except re.error:
    is_valid = False