[Python-ideas] Decorators on loops

[Masklinn]

On 2014-01-08, at 12:59 , Chris Angelico <rosuav at gmail.com> wrote:

> On Wed, Jan 8, 2014 at 10:21 PM, Enric Tejedor <enric.tejedor at bsc.es> wrote:
>> The basic idea would be to support decorators on loops, in addition to
>> functions and classes. Something like this:
>> 
>> @mydecorator
>> for i in range(10):
>>     # loop body
>> 
>> In mydecorator, I would like to have access to the loop body and the
>> iterable object.
>> 
>> In my case, I would use this to parallelize the iterations of the loop.
> 
> That's a nice theory, but the basic form of the decorator wouldn't
> work. Here's how decorators work on functions:
> 
> @foo
> def bar():
>    pass
> 
> is the same as:
> 
> def bar():
>    pass
> bar = foo(bar)
> 
> It depends on there being something assigned-to. With loops, that's
> not the case, so it's not possible to decorate them in the usual
> sense.
> 
> Can you turn your loop into a map() call? Something like this:
> 
> def loop_body(i):
>    # all the code for your loop body
> list(map(loop_body, range(10)))
> 
> Once you have it in that form, you can use multiprocessing.Pool() and
> its map() method, which will parallelize the loop for you (by
> distributing it over a pool of subprocesses). Would that cover what
> you need?

Alternatively, wrap the loop in a function and then do AST munging in
the decorator. Something similar (in spirit at least) to Numba
(http://numba.pydata.org).

You could even do something like immediate function invocation in the
decorator, and bind the result to the function name, although I'm not
sure your coworkers will like you.