inspect.Signature documentation incorrect on "parameters" parameter

[phemmer]

Bug report

Bug description:

The documentation states:

parameters
An ordered mapping of parameters’ names to the corresponding Parameter objects.

This is incorrect and it should actually be an iterable, as that is how the code treats it. If you pass it a mapping, the code will iterate over it, and only obtain the keys, and not the values.

import inspect

def foo(arg):
    ...

sig = inspect.signature(foo)

print(repr(sig.parameters))
sig.replace(parameters=sig.parameters)

mappingproxy(OrderedDict({'arg': <Parameter "arg">}))
Traceback (most recent call last):
  File "/tmp/test.py", line 9, in <module>
    sig.replace(parameters=sig.parameters)
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/inspect.py", line 3094, in replace
    return type(self)(parameters,
           ~~~~~~~~~~^^^^^^^^^^^^
                      return_annotation=return_annotation)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/inspect.py", line 3029, in __init__
    kind = param.kind
           ^^^^^^^^^^
AttributeError: 'str' object has no attribute 'kind'. Did you mean: 'find'?

Tested on 3.13.2

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[JelleZijlstra]

The documentation is for the attribute, not the constructor parameter; the two have different types. Perhaps the docs could be rewritten to make this clearer.

[skirpichev]

I think it's clear enough, more or less as for other classes. Sphinx docs have a dedicated paragraph for this argument: "The optional parameters argument is a sequence of Parameter objects, which is validated to check that there are no parameters with duplicate names, and that the parameters are in the right order, i.e. positional-only first, then positional-or-keyword, and that parameters with defaults follow parameters without defaults."

It's also obvious, that below documented attributes, not arguments of the Signature constructor. E.g. one has no empty argument.

[phemmer]

You're completely right.

The optional parameters argument is a sequence of Parameter objects

I think My eyes just snagged on the bold parameters text, and didn't pay enough attention. I think this can be closed.