while True or while 1

[BartC]

"Steve Holden" <steve at holdenweb.com> wrote in message 
news:mailman.462.1292214062.2649.python-list at python.org...
> On 12/12/2010 2:32 PM, Christian Heimes wrote:
>> Am 12.12.2010 19:31, schrieb Steve Holden:
>> $ python -m timeit -n20 -- "i = 0" "while 1:" "    i+=1" "    if i ==
>> 1000000: break"
>> 20 loops, best of 3: 89.7 msec per loop
>> $ python -m timeit -n20 -- "i = 0" "while True:" "    i+=1" "    if i ==
>> 1000000: break"
>> 20 loops, best of 3: 117 msec per loop

>> No argue with that! I was merely making a point that "while 1" executes
>> different byte code than "while True". Readability is important but
>> sometimes speed is of the essence. "while 1" is one of the few tricks to
>> speed up tight loops a bit.
>
> OK, but the figures you quote save you 27.3 ms per million iterations,
> for a grand total saving of 27.3 ns per iteration. So "a bit" is hardly
> worth considering for most programs, is it?

One these is 30% faster than the other. That's an appreciable difference, 
which you can't really just dismiss.

And you can't tell what the overall effect on a program will be: perhaps the 
loop will be in a library function , which might be called billions of 
times.

-- 
Bartc