71 lines
2.0 KiB
Python
71 lines
2.0 KiB
Python
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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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# args = []
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# if default is not _SENTINEL:
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# args.append(default)
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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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