python-3.x - Python3 if if else

Question

当我这样做时

x = "Hello"
if len(x) <= 9:
    print("The password must contain at least 9 letters")
if x[0].islower():
    print("The first password letter must be uppercase")
else:
    print("Password saved")
    password = x

我得到

>The password must contain at least 9 letters
>Password saved

我应该怎么做才能使程序停止：

>The password must contain at least 9 letters

Answer 1

在和elif之间使用：ifelse

x = "Hello"
if len(x) <= 9:
    print("The password must contain at least 9 letters")
elif x[0].islower():
    print("The first password letter must be uppercase")
else:
    print("Password saved")
    password = x

elif仅在未执行时才if执行，并且elif' 条件为真。您还可以根据elif需要链接任意数量的 s，在这种情况下，elif执行条件匹配的第一个。

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更新：由于 OP 在评论中说他希望一次显示所有错误，我会使用这样的东西：

x = "Hello"
errors = []
if len(x) <= 9:
    errors.append("The password must contain at least 9 letters")
if x[0].islower():
    errors.append("The first password letter must be uppercase")

if errors:
    print('\n'.join(errors))
else:
    print("Password saved")
    password = x

Answer 2

问题是代码中有两个 if 过滤器。我假设您想要一个结构，如果两个条件都满足"The password must contain at least 9 letters"，"The first password letter must be uppercase"则可以返回两者。

但是，如果您不需要此功能，只需将第二个替换为ifan即可elif。

如果您需要此功能，请尝试以下操作：

x = "Hello"
if len(x) <= 9:
    print("The password must contain at least 9 letters")
if x[0].islower():
    print("The first password letter must be uppercase")
if len(x) >= 9 and x[0].isupper():
    print("Password saved")
    password = x

这只是添加了第三个 if 语句来测试前面的条件是否得到满足。