[英]How can I type hint an attribute in Python 3.5?
I have a class where I want the initial value of an attribute to be None
: 我有一个类,我希望属性的初始值为
None
:
class SomeClass:
def __init__(self):
self.some_attribute = None
How can I add type hinting, so that the IDE understands that some_attribute
is usually of the type AnotherClass
? 如何添加类型提示,以便IDE了解
some_attribute
通常是AnotherClass
类型?
In Python 3.5, you have to write 在Python 3.5中,你必须写
self.some_attribute = None # type: AnotherClass
Since Python 3.6, new type hinting syntax was added for variables ( PEP 526 ): 从Python 3.6开始,为变量添加了新的类型提示语法( PEP 526 ):
self.some_attribute: AnotherClass = None
This will probably make every type-checking system complain, because None is in fact not an instance of AnotherClass. 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。 Instead, you can use
typing.Union[None, AnotherClass]
, or the shorthand: 相反,您可以使用
typing.Union[None, AnotherClass]
或简写:
from typing import Optional
...
self.some_attribute: Optional[AnotherClass] = None
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