On 12/1/2018 8:07 PM, Greg Ewing wrote:
Steven D'Aprano wrote:
After defining a separate iterable mapview sequence class
For backwards compatibilty reasons, we can't just make map() work like
this, because that's a change in behaviour.
Actually, I think it's possible to get the best of both worlds.
I presume you mean the '(iterable) sequence' 'iterator' worlds. I don't
think they should be mixed. A sequence is reiterable, an iterator is
once through and done.
Consider this:
from operator import itemgetter
class MapView:
def __init__(self, func, *args):
self.func = func
self.args = args
self.iterator = None
def __len__(self):
return min(map(len, self.args))
def __getitem__(self, i):
return self.func(*list(map(itemgetter(i), self.args)))
def __iter__(self):
return self
def __next__(self):
if not self.iterator:
self.iterator = map(self.func, *self.args)
return next(self.iterator)
The last two (unnecessarily) restrict this to being a once through
iterator. I think much better would be
def __iter__: return map(self.func, *self.args)
--
Terry Jan Reedy
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