[Python-Dev] NamedTuple (was: Py2.6 ideas) (original) (raw)

python at rcn.com python at rcn.com
Tue Feb 20 18:59:08 CET 2007

[Raymond Hettinger]

The constructor signature ... Point(*fetchall(s)), and it allows for direct construction with Point(2,3) without the slower and weirder form: Point((2,3)).

[Jim Jewett]

If you were starting from scratch, I would agree whole-heartedly; this is one of my most frequent mistakes.The question is whether it makes sense to "fix" NamedTuple without also fixing regular tuple, list,

Yes. Tuples and lists both have syntactic support for direct construction and NamedTuples aspire to that functionality:

vec = (dx3.0, dydx/dz, dz) # Regular tuple vec = Vector(dx3.0, dydx/dz, dz) # Named tuple

I've worked with the current version of the recipe for a long time and after a while the wisdom of the signature becomes self-evident. We REALLY don't want: vec = Vector((dx3.0, dydx/dz, dz)) # yuck For conversion from other iterables, it is REALLY easy to write: vec = Vector(*partial_derivatives)

Remember, list() and tuple() are typically used as casts, not as direct constructors. How often do you write: dlist = list((dx3.0, dydx/dz, dz)) That is usually written: dlist = [dx3.0, dydx/dz, dz] I think the Vec((dx, dy, dz)) sysntax falls into the category of foolish consistency.

Raymond

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