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