检查False的正确方法是什么? [英] what is the correct way to check for False?

问题描述

哪个更好? (为什么?)

Which is better? (and why?)

if somevalue == False:

或

if somevalue is False:

如果somevalue是字符串，您的答案会更改吗?

Does your answer change if somevalue is a string?

推荐答案

它取决于somevalue的含义:如果somevalue可以是任何东西，则可以检查它是否是布尔值和not:

It rather depends on what somevalue can be: if somevalue could be anything you could check that it's a boolean and not:

if isinstance(somevalue, bool) and not somevalue

这不依赖于False是单身人士.如果始终是单身人士，您也可以执行以下操作:

this doesn't rely on False being a singleton. If it always is a singleton you can also do:

if somevalue is False

---

但是 Python的PEP8声明您不必关心该类，而只需使用:

---

But PEP8 of Python states you shouldn't care if it about the class and just use:

if not somevalue

这将评估somevalue是否为"falsy".请参阅有关真值测试的Python文档.

this will evaluate if somevalue is "falsy". See Python documentation on Truth value testing.

PEP8状态:

请勿使用==将布尔值与True或False进行比较.

Don't compare boolean values to True or False using == .

并给出以下示例:

Yes:   if greeting:
No:    if greeting == True:
Worse: if greeting is True:

根据您的情况将其翻译为:

which translates in your case to:

Yes:   if not greeting:
No:    if greeting == False:
Worse: if greeting is False:

请记住，除了空字符串''外，每个字符串都被认为是真实的".

Keep in mind that each string is considered "truthy" except the empty string ''.

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