On 22.04.20 06:43, Soni L. wrote:
On 2020-04-21 7:12 p.m., Steven D'Aprano wrote:
On Tue, Apr 21, 2020 at 05:33:24PM -0300, Soni L. wrote:
> 1. see the other thread (strict zip), especially the parts where
they > brought up the lack of peekable/unput iterators in the context
of > getting a count out of an iterator.
I've seen it, as far as I can tell there are already good solutions
for getting a count out of an iterator.
are there *any* solutions for getting partial results out of zip with
different-length iterators of unknown origin?
You can basically use the code from this StackOverflow answer (code
attached below) to cache the last object yielded by each iterator:
https://stackoverflow.com/a/61126744
iterators = [
iter([0, 1, 2]),
iter([3, 4]),
iter([5]),
iter([6, 7, 8])
]
iterators = [cache_last(i) for i in iterators]
print(list(zip(*iterators))) # [(0, 3, 5, 6)]
partial = []
for i in iterators:
try:
partial.append(i.last)
except StopIteration:
break
print(partial) # [1, 4]
This is the code for `cache_last`:
class cache_last:
def __init__(self, iterable):
self.obj = iterable
self._iter = iter(iterable)
self._sentinel = object()
@property
def last(self):
if self.exhausted:
raise StopIteration
return self._last
@property
def exhausted(self):
if not hasattr(self, '_last'):
raise ValueError('Not started!')
return self._last is self._sentinel
def __next__(self):
try:
self._last = next(self._iter)
except StopIteration:
self._last = self._sentinel
raise
return self._last
def __iter__(self):
return self
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