python用户名正则只允许数字字母下划线组合，且不能以数字下换线开头，不能有中文和特殊字符。

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import re

Name = "_admin"
NUM_LETTER = re.compile("^(?!\d+$)[\da-zA-Z_]+$")     #数字和字母组合，不允许纯数字
FIRST_LETTER = re.compile("^[a-zA-Z]")           #只能以字母开头

def account_name_fomart(Name):
    if NUM_LETTER.search(Name):
       if FIRST_LETTER.search(Name):
           return True
    return False

def is_account_name_fomart(Name):
	if not account_name_fomart(Name):
    	msg = "用户名不合法"
    	return msg