请问以下代码为什么编译通过了,但是没有输出
current_users=["Amy","Tom","Jack","小明","小红"]
new_users=["Jack","A","B","C","Tom"]
for new_user in new_users:
a=0
for current_user in current_users:
if new_user.lower()==current_user.lower():
a==1
if a==1:
print(new_user+" has been used.")