On 2010-02-18 17:36 PM, Stephen Hansen wrote:
On Thu, Feb 18, 2010 at 2:56 PM, Robert Kern <robert.k...@gmail.com
<mailto:robert.k...@gmail.com>> wrote:
class once(object):
def __init__(self, func, *args, **kwds):
self.func = func
self.args = args
self.kwds = kwds
def __iter__(self):
return self
def next(self):
self.func(*self.args, **self.kwds)
raise StopIteration()
Hmm, yeah. I'd probably tweak it into a decorator and name it
sideeffect_only or something, but yeah, that's the right approach at least.
Well, with a decorator, you could even use the cringeworthy return/yield syntax
while keeping it hidden from your users (not to mention reducing the amount of
boilerplate people need to write).
from functools import wraps
def sideeffect_only(func):
@wraps(func)
def wrapper(*args, **kwds):
func(*args, **kwds)
# Some helpful comment about why there is a return/yield.
return
yield
return wrapper
But you can also write one where the wrapper() returns a once() instance. It
might be useful to use the once class instead of a generator such that you can
write code that distinguishes side-effect only iterators from other iterators in
your system. It might be useful for debugging if nothing else.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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