Python正则表达式来确定字符是数字，字母数字还是指定的字符串

Question

I am unsure as to how one would use a Python regex to determine whether a character is numeric, alphanumeric or in a specified string.

Something like (fake code warning):

if 'a' in re.['A-Z']:
   print "Alpha"

if '.' in re.['.,;']:
   print "Punctiation"

Answer 1

Use str.isalpha() method:

>>> 'a'.isalpha()
True

For testing single character for punctuation or alphanumeric, you can use constants pre-defined in string module:

>>> '.' in string.punctuation:
True

Answer 2

You can use the match function from module re :

import re

x = 'a'
if re.match('[a-zA-Z]', x):
    print "Alpha"