Rationale for different signatures of tuple.__new__ and namedtuple.__new__
Hi, 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__? IPython's serialization code depends on a tuple's __new__() having the signature that tuple has and therefore does not work with namedtuples. See discussion here: http://article.gmane.org/gmane.comp.python.general/726849 Thanks, John.
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)
Later today you posted "Differences creating tuples and collections.namedtuples" on python-list. http://thread.gmane.org/gmane.comp.python.general/726849 That *is* the proper place to make observations about current Python and ask questions about why it is the way it is and how to work around features that get in your way. So I will answer there, if I think more needs to be said, after reading the multiple current responses. Anyone else should do the same. -- Terry Jan Reedy
participants (3)
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Hrvoje Niksic -
John Reid -
Terry Reedy