Is there an peekable similar to peekable but in additional allowing one to put some data to it?
Ian Kelly
ian.g.kelly at gmail.com
Wed Jan 11 12:07:35 EST 2017
On Wed, Jan 11, 2017 at 8:51 AM, Peng Yu <pengyu.ut at gmail.com> wrote:
> Hi, peekable from more-itertools only allow peeking an iterator. But
> sometimes, one may want to take a look at an element, manipulate it,
> then put it back to the iterator. Is there a class in python that can
> help do this?
Not that I'm aware of, but maybe this recipe will help.
from collections import deque
class PushIterator:
def __init__(self, iterable, push=()):
self._iter = iter(iterable)
self._pushed = deque(push)
self._stopped = False
def push(self, item):
if self._stopped:
raise RuntimeError('Cannot push onto exhausted iterator')
self._pushed.append(item)
def __iter__(self):
return self
def __next__(self):
if self._pushed:
return self._pushed.pop()
try:
return next(self._iter)
except StopIteration:
self._stopped = True
raise
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