How not to miss the next element after itertools.takewhile()

Question

Say we wish to process an iterator and want to handle it by chunks.
The logic per chunk depends on previously-calculated chunks, so groupby() does not help.

Answer 1

Given the callable GetNewChunkLogic() will report True along first chunk and False afterward.
The following snippet

1. solves the 'additional next step' problem of takewhile .
2. is elegant because you don't have to implement the back-one-step logic .

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def partition(pred, iterable):
    'Use a predicate to partition entries into true entries and false entries'
    # partition(is_odd, range(10)) -->  1 3 5 7 9 and 0 2 4 6 8
    t1, t2 = tee(iterable)
    return filter(pred, t1), filterfalse(pred, t2)

while True:
    head, tail = partition(GetNewChunkLogic(), myIterator)
    process(head)
    myIterator = tail

However, the most elegant way is to modify your GetNewChunkLogic into a generator and remove the while loop.