import re
m = re.search(r'\d+$', string)
# if the string ends in digits m will be a Match object, or None otherwise.
if m is not None:
    print m.group()

\d 匹配一个数字，\d+ 表示匹配一个或多个数字(贪婪:匹配尽可能多的连续数字).而 $ 表示匹配字符串的结尾.

\d matches a numerical digit, \d+ means match one-or-more digits (greedy: match as many consecutive as possible). And $ means match the end of the string.