[Python-Dev] Impact of Namedtuple on startup time

[Steven D'Aprano]

On Tue, Jul 18, 2017 at 01:17:24AM +0200, Giampaolo Rodola' wrote:

> The extra memory overhead is a price I would be happy to pay considering
> that collections.namedtuple is considerably slower than a plain tuple.
> Other than the additional overhead on startup / import time, instantiation
> is 4.5x slower than a plain tuple:
> 
>     $ python3.7 -m timeit -s "from collections import namedtuple; nt =
> namedtuple('xxx', ('x', 'y'))" "nt(1, 2)"
>     1000000 loops, best of 5: 313 nsec per loop
> 
>     $ python3.7 -m timeit "tuple((1, 2))"
>     5000000 loops, best of 5: 68.4 nsec per loop

I don't think that is a fair comparision. As far as I can tell, that 
gets compiled to a name lookup for "tuple" which then returns its 
argument unchanged, the tuple itself being constant-folded at compile 
time.

py> dis.dis("tuple((1, 2))")
  1           0 LOAD_NAME                0 (tuple)
              3 LOAD_CONST               2 ((1, 2))
              6 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
              9 RETURN_VALUE


-- 
Steve