[Python-Dev] Rationale for different signatures of tuple.__new__ and namedtuple.__new__

[Hrvoje Niksic]

On 02/18/2013 03:32 PM, John Reid wrote:
> I can do
>
> tuple([1,2,3])
>
> but not:
>
> from collections import namedtuple
> namedtuple('B', 'x y z')([1,2,3])
>
> I get a TypeError: __new__() takes exactly 4 arguments (2 given)
> However I can do:
>
> namedtuple('B', 'x y z')._make([1,2,3])
>
> So namedtuple's _make classmethod looks a lot like tuple's __new__().
> What's the rationale for this? Wouldn't it be better to share the same
> signature for __new__?

Sharing the constructor signature with tuple would break the common case of:

namedtuple('B', 'x y z')(1, 2, 3)