[Python-ideas] Adding "Typed" collections/iterators to Python

Terry Reedy tjreedy at udel.edu
Wed Dec 21 02:09:12 CET 2011

On 12/20/2011 7:09 PM, Steven D'Aprano wrote:
> Terry Reedy wrote:
>> 2.) there are serious dragons in
>>> how python handles complex inheritance graphs that result in
>>> "object.__new__() takes no parameters", despite not having any builtin
>>> bases and having no base class overriding __new__ or __init__
>> Best not to use object as the apex of multiple inheritance.
> Is that possible in Python 3?

I believe the recommendation I have seen is something like this

 >>> class C():
	def __init__(self, *arg, **kwds): pass
 >>> C(1)
<__main__.C object at 0x00000000034C0F98>

 >>> object(1)
Traceback (most recent call last):
   File "<pyshell#2>", line 1, in <module>
TypeError: object.__new__() takes no parameters

Now, so others have posted, define A and B with super, inheriting from C 
instead of object, and D with super inheriting from A and B, and all 
should go well instead of crashing. But I have not tested this myself. 
Same for ordinary single inheritance chain.

Terry Jan Reedy

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