On Fri, Jan 24, 2014 at 08:07:43PM -0800, Larry Hastings wrote:
>
> (Quick, because apparently nobody reads the long ones!)
>
> In Python 3.3:
>
> >>> class C:
> ... def foo(self, a): pass
> ...
> >>> c = C()
> >>> help(c.foo)
>
> shows you the signature "foo(self, a)".
That matches the function declaration as defined right there in the
class.
> As in, it claims it accepts two
> parameters. The function actually only accepts one parameter, because
> "self" has already been bound.
No, that's wrong. The *function* C.foo accepts two parameters, self and
a, exactly as declared. The *method* c.foo accepts only one.
> inspect.signature gets this right:
>
> >>> import inspect
> >>> str(inspect.signature(c.foo))
> '(a)'
>
> but inspect.getfullargspec does not:
>
> >>> inspect.getfullargspec(c.foo)
> FullArgSpec(args=['self', 'a'], varargs=None, varkw=None,
> defaults=None, kwonlyargs=[], kwonlydefaults=None, annotations={})
That's arguable. Should inspect give the argument spec of the method
object or the function object? I can see arguments for both.
Backwards-compatibility argues against changing either, though.
help() is another story. Since help() is documentation aimed at the
end-user, we can change it without worrying about backward
compatibility. Ideally, help() ought to distingush between the two
cases. I see that it already does, but not very well.
help(c.foo) in Python 3.3 gives:
Help on method foo in module __main__:
foo(self, a) method of __main__.C instance
while help(C.foo) gives:
Help on function foo in module __main__:
foo(self, a)
I think in the bound method case, it should drop the "self":
Help on method foo in module __main__:
foo(a) method of __main__.C instance
and in the function (previously: unbound method) case, it should show
the "self" and the class:
Help on function foo in module __main__:
foo(self, a) method of class __main__.C
although I'm not sure how that second one is possible, now that unbound
methods are gone and C.foo returns a plain function.
(Hmmm, perhaps getting rid of unbound methods was a mistake...)
> A) pydoc and help() should not show bound parameters in the signature,
> like inspect.signature.
> B) pydoc and help() should show bound parameters in the signature, like
> inspect.getfullargspec.
Provided they are described as *methods* rather than *functions*, bound
methods should not show self. Likewise for classmethod and cls. That is,
I'm voting +1 on A provided help() doesn't confuse methods and
functions.
--
Steven
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