#_*_coding:utf-8_*_
#__author__ = "csy"
import random
checkcode=‘‘
for i in range(4):
    current=random.randrange(0,4)   #生成随机数与循环次数比对
    current1 = random.randrange(0,4)
    if current == i:
        tmp=chr(random.randint(65,90))   #65~90为ASCii码表A~Z
    elif current1 == i:
        tmp = chr(random.randint(97,122))   #97~122为ASCii码表a~z
    else:
        tmp=random.randint(0,9)
    checkcode+=str(tmp)
print(checkcode)