主题： typing

• Protocol classes: structural typing for duck-typed Python

  A typing.Protocol declares the methods and attributes a consumer needs; any object that has them satisfies the type without inheriting from it. Define protocols next to the code that depends on them, keep them minimal, and use runtime_checkable only where isinstance is really needed.

  article · en · reviewed · 知识截至 2026-09-15

• Iterables versus iterators: the protocol behind for loops

  An iterable returns a fresh iterator from __iter__; an iterator returns items from __next__, raises StopIteration when done and must keep raising it. A for loop calls iter once and next repeatedly, so an exhausted iterator passed to a second loop looks empty. Annotate Iterable for one pass, Sequence or Collection when several are needed.

  article · en · reviewed · 知识截至 2026-09-15

• 使用 TypeVar、ParamSpec 和 PEP 695 语法编写泛型函数与装饰器

  类型变量关联参数与返回值的类型；PEP 695 的方括号语法（def f[T](...)）取代手工声明 TypeVar，上界与类型约束的语义不同，而 ParamSpec 让装饰器保留所包装函数的签名，不再将其抹去为 Callable[..., Any]。

  article · zh · reviewed · 知识截至 2026-09-15

机器可读： JSON