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David Beazley in his tutorial pointed out that you could use a metaclass to create function signatures for the common use case of:
class foo:
 def __init__(self, name, value, high, low):
 self.name = name
 self.value = value
 [...]
The signature can be used so that the classes created using an automation metaclass will show a signature of "(*args)". inspect.signature will use this signature, but "help()" will not use the signature.
This is a stub created during the tutorial, I will flesh it out further during the sprints.

This might be a duplicate of issue17053, but the patch provided there doesn't resolve the issue, at least as far as I know it. Here is an example, from David Beazley's talk at PyCon 2013:
from inspect import Parameter, Signature
def make_signature(names):
 return Signature(
 Parameter(name, Parameter.POSITIONAL_OR_KEYWORD) for name in names)
class Structure:
 __signature__ = make_signature([])
 def __init__(self, *args, **kwargs):
 bound = self.__signature__.bind(*args, **kwargs)
 for name, val in bound.arguments.items():
 setattr(self, name, val)
class Stock(Structure):
 __signature__ = make_signature(['name', 'shares', 'price'])
pyth = Stock('PYTH', 100, 50)
help(pyth.__init__)
Which produces:
__init__(self, *args, **kwargs) method of __main__.Stock instance
Instead of:
__init__(self, name, shares, price) method of __main__.Stock instance

If I read the code correctly help(pyth.__init__) won't use the __signature__ because that is an attribute of the type, not of the method itself. 
With the patch in issue17053 help should be better when __init__'s signatuer is set explicitly:
class Stock(Structure):
 __signature__ = make_signature(['name', 'shares', 'price'])
 def __init__(self, *args, **kwds):
 super(Stock, self).__init__(*args, **kwds)
 __init__.__signature__ = __signature__
Sadly enough it isn't easily possible to define a subclass of function where __signature__ is a property that returns the class attribute __signature__.

issue17053 was closed in favour of issue19674 but I don't know if this issue is a duplicate of the former anyway.

Since 3.4, help() uses signature.
Closing this one.