如 help(foo) 所示,Python 方法签名中的正斜杠“/”是什么意思?

What is the meaning of a forward slash "/" in a Python method signature, as shown by help(foo)?

help(foo)交互返回的签名中,一个/是什么意思?

In [37]: help(object.__eq__)

Help on wrapper_descriptor:

__eq__(self, value, /)
    Return self==value.

In [55]: help(object.__init__)

Help on wrapper_descriptor:

__init__(self, /, *args, **kwargs)
    Initialize self.  See help(type(self)) for accurate signature.

我认为这可能与仅关键字参数有关,但事实并非如此。当我使用仅关键字参数创建自己的函数时,位置参数和仅关键字参数由 *(如预期)分隔,而不是 // 是什么意思?

here, the / as an argument marks the end of arguments that are positional only (see here 所述),即不能用作关键字参数的参数。在 __eq__(self, value, /) 的情况下,斜杠在末尾,这意味着所有参数都被标记为位置,而在 __init__ 的情况下,只有自己,即什么都没有,只是位置。

编辑: 这以前仅用于内置函数,但 since Python 3.8, you can use this in your own functions. The natural companion of / is * which allows to mark the beginning of keyword-only arguments. Example using both

# a, b are positional-only
# c, d are positional or keyword
# e, f are keyword-only
def f(a, b, /, c, d, *, e, f):
    print(a, b, c, d, e, f)

# valid call
f(10, 20, 30, d=40, e=50, f=60)

# invalid calls:
f(10, b=20, c=30, d=40, e=50, f=60)   # b cannot be a keyword argument
f(10, 20, 30, 40, 50, f=60)           # e must be a keyword argument