如何在Python 3.5中键入hint属性? [英] How can I type hint an attribute in Python 3.5?

问题描述

我有一个要在其中将属性的初始值设为None的类:

I have a class where I want the initial value of an attribute to be None:

class SomeClass:
    def __init__(self):
        self.some_attribute = None

如何添加类型提示，以便IDE理解some_attribute通常是AnotherClass类型?

How can I add type hinting, so that the IDE understands that some_attribute is usually of the type AnotherClass?

推荐答案

在Python 3.5中，您必须编写

In Python 3.5, you have to write

self.some_attribute = None  # type: AnotherClass

从Python 3.6开始，为变量添加了新类型的提示语法( PEP 526 ):

Since Python 3.6, new type hinting syntax was added for variables (PEP 526):

self.some_attribute: AnotherClass = None

这可能会使每个类型检查系统都抱怨，因为None实际上不是AnotherClass的实例.相反，您可以使用 typing.Union[None, AnotherClass] 或速记:

This will probably make every type-checking system complain, because None is in fact not an instance of AnotherClass. Instead, you can use typing.Union[None, AnotherClass], or the shorthand:

from typing import Optional
...
self.some_attribute: Optional[AnotherClass] = None

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