Python猜数字游戏

import random
a = random.randint(1000,9999)
a = str(a)
print(a)
count = 0
b = input("请输入")
while a != b:
s = ''
for x in range(4):
if a[x] == b[x]:
s += b[x]
else:
s += 'x'
print(s)
count += 1
b = input("请输入")
print("猜对了！你一共猜了"+str(count)+"次")