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''' |
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This module provides a newnext() function in Python 2 that mimics the |
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behaviour of ``next()`` in Python 3, falling back to Python 2's behaviour for |
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compatibility if this fails. |
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``newnext(iterator)`` calls the iterator's ``__next__()`` method if it exists. If this |
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doesn't exist, it falls back to calling a ``next()`` method. |
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For example: |
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>>> class Odds(object): |
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... def __init__(self, start=1): |
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... self.value = start - 2 |
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... def __next__(self): # note the Py3 interface |
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... self.value += 2 |
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... return self.value |
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... def __iter__(self): |
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... return self |
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... |
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>>> iterator = Odds() |
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>>> next(iterator) |
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1 |
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>>> next(iterator) |
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3 |
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If you are defining your own custom iterator class as above, it is preferable |
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to explicitly decorate the class with the @implements_iterator decorator from |
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``future.utils`` as follows: |
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>>> @implements_iterator |
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... class Odds(object): |
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... # etc |
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... pass |
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This next() function is primarily for consuming iterators defined in Python 3 |
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code elsewhere that we would like to run on Python 2 or 3. |
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''' |
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_builtin_next = next |
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_SENTINEL = object() |
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def newnext(iterator, default=_SENTINEL): |
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""" |
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next(iterator[, default]) |
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Return the next item from the iterator. If default is given and the iterator |
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is exhausted, it is returned instead of raising StopIteration. |
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""" |
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try: |
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try: |
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return iterator.__next__() |
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except AttributeError: |
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try: |
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return iterator.next() |
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except AttributeError: |
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raise TypeError("'{0}' object is not an iterator".format( |
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iterator.__class__.__name__)) |
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except StopIteration as e: |
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if default is _SENTINEL: |
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raise e |
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else: |
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return default |
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__all__ = ['newnext'] |
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