What is the meaning of a forward slash “/” in a Py

Question

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Python: What does the slash mean in help() output? (3 answers)

Closed 4 years ago.

In the signature returned interactively by help(foo), what is the meaning of a /?

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.

I thought it might be related to keyword-only arguments, but it's not. When I create my own function with keyword-only arguments, positional and keyword-only arguments are separated by * (as expected), not by /. What does the / mean?

Answer 1

As explained here, the '/' as a parameter marks the end of parameters that are positional only (see here), i.e. parameters you can't use as keyword parameters. In the case of __eq__(self, value, /) the slash is at the end, which means that all parameters are marked as positional only while in the case of your __init__ only self is positional only.