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Subject: Re: Differences creating tuples and collections.namedtuples
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Xref: csiph.com comp.lang.python:39190

On Monday, February 18, 2013 6:09:16 AM UTC-8, John Reid wrote:
> I'm aware how to construct the namedtuple and the tuple. My point was
> that they use different syntaxes for the same operation and this seems
> to break ipython. I was wondering if this is a necessary design feature
> or perhaps just an oversight on the part of the namedtuple author or
> ipython developers.

It was not an oversight on the part of the namedtuple author.
It was a deliberate design decision to improve usability for
named tuple's primary use case.

Consider a namedtuple such as:

     Person =3D namedtuple('Person', ['name', 'rank', 'serial_number'])

With the current signature, instances can be created like this:

    p =3D Person('Guido', 'BDFL', 1)

If instead, the __new__ signature matched that of regular tuples,
you would need to write:

   p =3D Person(('Guido', 'BDFL', 1))

The double parens are awkward.  You would lose tooltips that prompt you for=
 Person(name, rank, serial_number).  You would lose the ability to use keyw=
ord arguments such as Person(rank=3D'BDFL', serial_number=3D1, name=3D'Guid=
o') or Person(**d).  The repr for the namedtuple would lose its eval(repr(t=
)) roundtrip property. =20

If your starting point is an existing iterable such as s=3D['Guido', 'BDFL'=
, 1], you have a couple of choices:   p=3DPerson(*s) or p=3DPerson._make(s)=
.  The latter form was put it to help avoid unpacking and repacking the arg=
uments.  =20


Raymond