The "loop and a half"
Paul Moore
p.f.moore at gmail.com
Wed Oct 4 10:01:55 EDT 2017
On 4 October 2017 at 14:02, Robin Becker <robin at reportlab.com> wrote:
> On 04/10/2017 11:57, Rhodri James wrote:
>>
>> On 04/10/17 10:01, Robin Becker wrote:
>>>
>>> Given the prevalence of the loop and a half idea in python I wonder why
>>> we don't have a "do" or "loop" statement to start loops without a test.
>>
>>
>> See PEP 315. Guido's rejection note is here:
>> https://mail.python.org/pipermail/python-ideas/2013-June/021610.html
>>
> seems fair enough; I suppose the cost is negligible or perhaps there's
> peephole optimization for this common case.
There is:
>>> def f():
... while True:
... pass
...
>>> import dis
>>> dis.dis(f)
2 0 SETUP_LOOP 4 (to 6)
3 >> 2 JUMP_ABSOLUTE 2
4 POP_BLOCK
>> 6 LOAD_CONST 0 (None)
8 RETURN_VALUE
Paul
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