Python3 中函数声明的“->”是什么意思?

What does '->' mean with function declaration in Python3?

最近在学习函数声明的时候遇到了Python3中的'->',这是什么意思?到目前为止,除了 Javascript 函数声明之外,我从未见过这样的声明。

def f(self, s: 'str') -> 'bool':
    pass

根据 python docs 相关的打字。

This is the python typing feature, which let you specify the return type of functions in python

这是 return 函数值类型的注解。

def sum() -> expression:

That is, the parameter list can now be followed by a literal -> and a Python expression. Like the annotations for parameters, this expression will be evaluated when the function definition is executed.

https://www.python.org/dev/peps/pep-3107/