Numeric coercions

[Joshua Landau]

On 7 July 2013 05:48, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> On Sun, 07 Jul 2013 05:17:01 +0100, Joshua Landau wrote:
>
>> On 7 July 2013 04:56, Steven D'Aprano
>> <steve+comp.lang.python at pearwood.info> wrote:
> ...
>>> def promote(x):
>>>     if isinstance(x, str): raise TypeError return float(x)
>
>>>>> from operator import methodcaller
>>>>> safe_float = methodcaller("__float__")
>
> Nice!
>
> That's almost as fast as calling float. That will probably do :-)

*Almost* as fast?

%~> \python -m timeit -s "safe_float =
__import__('operator').methodcaller('__float__'); n = 423.213"
"float(n)"
1000000 loops, best of 3: 0.398 usec per loop
%~> \python -m timeit -s "safe_float =
__import__('operator').methodcaller('__float__'); n = 423.213"
"safe_float(n)"
1000000 loops, best of 3: 0.361 usec per loop

%~> \python -m timeit -s "safe_float =
__import__('operator').methodcaller('__float__'); n = 423" "float(n)"
1000000 loops, best of 3: 0.468 usec per loop
%~> \python -m timeit -s "safe_float =
__import__('operator').methodcaller('__float__'); n = 423"
"safe_float(n)"
1000000 loops, best of 3: 0.436 usec per loop

Actually, it's a fair bit faster (yes, I am purposely not showing you
the results for Decimals).