On 3/27/2011 7:53 AM, Jan Kaliszewski wrote:
Which one of the following do you prefer?
* filter((lambda x: x is None), iterable) * filter(functools.partial(operator.is_, None), iterable)
These two produce an iterable of Nones, one for each None in the original iterable. I have trouble imagining a real use case for this. I can see a use cases for dropping everything but None. This can, of course, always be done at the point of use: for ob in iterable: if ob is not None: do_something(ob) If you want to separate the conditional from the action and hide the conditional, then write a trivial, specific, filter generator: def dropNone(it): for ob in it: if ob is not None: yield ob for ob in dropNone(iterable): do_something(ob) For repeated use, I prefer dropNone to any filter version, including your proposal.
* filter(None, (x is None for x in iterable))
This is not the same thing as the above as it instead produces an iterable of Trues, one for each None in iterable. -- Terry Jan Reedy