Raymond Hettinger <[email protected]> added the comment:
> Right now, you really gotta jump through hoops
> in some cases if you only want to use __new__
> and don't care about __init__
I'm now sure I see the difficulty. It is easy to define a classes with __new__
and without __init__:
>>> class A:
def __new__(cls, *args):
print('New called with', cls, 'and', args)
return object.__new__(cls)
>>> a = A(10, 20, 30)
New called with <class '__main__.A'> and (10, 20, 30)
>>> isinstance(a, A)
True
> Like __hash__, allow setting MyClass.__init__ to None
FWIW, the API for hashing being set-to-None wasn't done because we like it
(there a numerous downsides). It was done because we needed hashing to be on by
default and there needed to be a way to turn it off. The downsides are that it
confuses users, it is hard to teach and remember, and it adds a branch to
various APIs which would then need to test for None. Instead, we prefer the
pattern of having object() provide a default dummy method that either does
nothing or gives up (like object.__init__ or the various rich comparison
methods for object). This simplifies downstream code than doesn't have to
check for a rare special case.
----------
assignee: -> rhettinger
nosy: +rhettinger
_______________________________________
Python tracker <[email protected]>
<https://bugs.python.org/issue34314>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
