# 随机4位验证码
def yanzhengma():
	strvar = ""
	for i in range(4):
		# 产生大写字母A~Z
		bchr = chr(random.randrange(65,91))
		# 产生小写字母a~z
		schr = chr(random.randrange(97,123))
		# 数字0~9
		num = str(random.randrange(0,10))
		# 把所有随机值得种类塞到列表里
		listvar = [bchr,schr,num]
		# 随机选取一个
		res = random.choice(listvar)
		# 拼接字符串
		strvar += res
	# 返回字符串
	return strvar
res = yanzhengma()
print(res)