Python3中的三个点点点(Ellipsis)

curry_du

于 2020-07-09 00:14:40 发布

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分类专栏： python 文章标签： python

本文链接：https://blog.youkuaiyun.com/curry_du/article/details/107217609

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平时翻阅源码的时候可能会遇到过这样的函数定义。点。点。点（Ellipsis对象，py2中没有这个...语法）

def main(module: Union[None, str, ModuleType] = ...,
         defaultTest: Union[str, Iterable[str], None] = ...,
         argv: Optional[List[str]] = ...,
         testRunner: Union[Type[TestRunner], TestRunner, None] = ...,
         testLoader: TestLoader = ..., exit: bool = ..., verbosity: int = ...,
         failfast: Optional[bool] = ..., catchbreak: Optional[bool] = ...,
         buffer: Optional[bool] = ...,
         warnings: Optional[str] = ...) -> TestProgram: ...

先看看是啥玩意

type(...)
<class 'ellipsis'>

原来是ellipsis，去查了下官方文档，发现这是个built-in constants，下面是文档的描述

Ellipsis

The same as the ellipsis literal “...”. Special value used mostly in conjunction with extended slicing syntax for user-defined container data types.