Coroutines and argument tupling

Bjoern Schliessmann usenet-mail-0306.20.chr0n0ss at spamgourmet.com
Thu Aug 16 11:40:54 CEST 2007


Marshall T. Vandegrift wrote:
> Without the decorator that becomes:
> 
>     gen = nextn(2)
>     print gen.next()  # => [0, 1]
>     print gen.send(3) # => [2, 3, 4]
>     print gen.send(1) # => [5]
> 
> The former is just that smidgen nicer, and allows you to continue
> to make use of argument defaults and varadic arguments if so
> desired.

The solution I'd use is a decorator that calls next automatically
one time after instantiation. Then you can use send normally, and
don't have to care about any initial parameters, which makes the
code clearer (initial parameters should be used for setup purposes,
but not for the first iteration, IMHO). It'd look like this (from
PEP 342, http://www.python.org/dev/peps/pep-0342/):

def consumer(func):
    def wrapper(*args,**kw):
        gen = func(*args, **kw)
        gen.next()
        return gen
    wrapper.__name__ = func.__name__
    wrapper.__dict__ = func.__dict__
    wrapper.__doc__  = func.__doc__
    return wrapper

@consumer
def nextn():
    ...

gen = nextn()
print gen.send(2) # => [0, 1]
print gen.send(3) # => [2, 3, 4]
print gen.send(1) # => [5]

Regards,


Björn

-- 
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system has been recalled




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