Repository navigation
Add support for multiple signatures #73536
Description
Activity
Some functions can be described by the single signature. See examples in msg285647. Selected examples:
dict.pop(key) dict.pop(key, default) type(obj) type(name, bases, mapping) range(stop) range(start, stop, step=1) min(iterable, *, key=identity) min(iterable, *, default, key=identity) min(*args, key=identity)
I think the only way to resolve this problem is to add the support of multiple signatures in inspect, pydoc, Argument Clinic, etc.
Signature object provides methods like .bind(), which will be hard to define if a function has many signatures. Also, inspect.signature currently returns one Signature object, that shouldn't be changed.
Wouldn't it be easier instead of this:
type(obj)
type(name, bases, mapping)do this:
type(obj_or_name, bases=None, mapping=None)And explain what really is going on in the docstring?
It can be do, but I don't think it is worth. Making bases and mapping optional arguments does not make much sense to me. And there is no a value that can be used as a default value for the second parameter in dict.pop().
#117671 is a draft implementation. It adds MultiSignature, which is a subclass of Signature, but supports iteration and has length.
inspect.signatures()always returns a MultiSignature, even if it contains a single signature.inspect.signature()can also return a MultiSignature.pydocand all other stdlib code was updated to support multisignatures. All builtin functions and methods of builtin classes excepttype()andsuper()has now signatures, i.e. are supported byinspect.signature()andinspect.signatures().>>> import inspect >>> inspect.signature(range) <MultiSignature (stop, /)|(start, stop, step=1, /)> >>> print(inspect.signature(range)) (stop, /) (start, stop, step=1, /) >>> >>> inspect.signature(dict.pop) <MultiSignature (self, key, /)|(self, key, default, /)> >>> print(inspect.signature(dict.pop)) (self, key, /) (self, key, default, /) >>> >>> inspect.signature(min) <MultiSignature (iterable, /, *, key=None)|(iterable, /, *, default, key=None)|(arg1, arg2, /, *args, key=None)> >>> print(inspect.signature(min)) (iterable, /, *, key=None) (iterable, /, *, default, key=None) (arg1, arg2, /, *args, key=None)
MultiSignature's attribute
parametersis a union of all parameters in all subsignatures, andreturn_annotationis a union of return annotations of subsignatures.bind()andbind_partial()are supported, butreplace()does not.Future features:
- Union and itersection of Signature and MultiSignature objects. An intersection will be useful to find the common signature for
__new__and__init__methods (one of them can contain*args, **kwargs). - Partial signature. Like
bind_partial(), but instead of a BoundArguments object it should return a new (multi-)signature object after binding arguments. It will help to get the signature of bound and class methods,partialandpartialmethodobjects. - Generate multi-signatures in Argument Clinic if default values are not representable.
- Generate multi-signatures in Argument Clinic for optional groups.
- Support multi-signatures in
functools.singledispatchandtyping.override().
Reacted by Erlend E. Aasland, Sergey B Kirpichev and Kirill Podoprigora- Union and itersection of Signature and MultiSignature objects. An intersection will be useful to find the common signature for
IMO, this should be a PEP.
It's an exciting improvement, and it has a wide reach -- areas like typing, dynamic dispatch, or documentation will all be affected.Reacted by Stan Ulbrych- changed the title
[-]Add support of multiple signatures[/-][+]Add support for multiple signatures[/+]on Apr 4, 2025 - marked The docstring of
dict()should match the doc ofdict()and it should be more understandable #137629 as a duplicate of this issueon Sep 2, 2025
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
Show more details
GitHub fields:
bugs.python.org fields:
Linked PRs