[Python-ideas] namedtuple with ordereddict

Tim Peters tim.peters at gmail.com
Wed Jul 19 11:20:38 EDT 2017

[Giampaolo Rodola' <g.rodola at gmail.com>]
> Still much slower (-4.3x) than plain tuples though:
> $ python3.7 -m timeit -s "import collections; Point => collections.namedtuple('Point', ('x', 'y'));" "Point(5, 11)"
> 1000000 loops, best of 5: 313 nsec per loop
> $ python3.7 -m timeit "tuple((5, 11))"
> 5000000 loops, best of 5: 71.4 nsec per loop

I believe this was pointed out earlier:  in the second case,

1. (5, 11) is built at _compile_ time, so at runtime it's only
measuring a LOAD_FAST to fetch it from the code's constants block.

2. The tuple() constructor does close to nothing when passed a tuple:
it just increments the argument's reference count and returns it.

>>> t = (1, 2)
>>> tuple(t) is t

In other words, the second case isn't measuring tuple _creation_ time
in any sense:  it's just measuring how long it takes to look up the
name "tuple" and increment the refcount on a tuple that was created at
compile time.

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