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Previous and next values inside a loop https://stackoverflow.com/questions/1011938/python-previous-and-next-values-inside-a-loop/1012089#1012089
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| from itertools import tee, islice as slice, chain, izip as zip | |
| def previous_and_next(iterable, fill_value=None): | |
| prevs, items, nexts = tee(iterable, 3) | |
| prevs = chain([fill_value], prevs) | |
| nexts = chain(slice(nexts, 1, None), [fill_value]) | |
| return zip(prevs, items, nexts) |
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