我编写了一段简单的Python代码，该代码应该将列表current_usernames（正在尝试登录的usernames用户）与列表（已经登录的用户）进行比较。如果来自的用户current_usernames已加入usernames，则该用户将被拒绝，否则将招呼该用户。如果在没有用户current_usernames，应该只有一个输出说：There are no users in the system at this point。
代码：
usernames = ["User1", "User2", "User3", "User4", "User5", "Admin"]
current_usernames = ["User6", "User7", "User3", "User8", "User5"]
for current_user in current_usernames:
if current_user not in usernames:
if current_user == "Admin":
print("Hello Admin!!! Welcome back!")
else:
print("Hello " + current_user)
else:
print("Sorry, " + current_user + " is already logged in.")
else:
print("There are no users in the system at this point!")
输出：
Hello User6
Hello User7
Sorry, User3 is already logged in.
Hello User8
Sorry, User5 is already logged in.
There are no users in the system at this point!
题：
为什么for循环There are no users in the system at this point!在循环结束时返回？
我期望for循环在之后停止，Hello User5因为current_usernames左侧没有更多用户了。
循环的else子句for在循环正常完成的任何时间触发，而不是通过break语句触发。由于您的循环不包含break，因此else总是会触发。
else子句背后的想法是使编写线性搜索之类的内容变得更加容易：
for x in sequence:
if x == key:
print('found it')
break
else:
print('Not found')
似乎您混淆了else以下for循环，而else通常在条件语句中发现以下内容可以满足您的要求：
if current_users:
for current_user in current_usernames:
...
else:
print('No users currently trying to get into the system')
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