Viewing file:  newnext.py (1.97 KB) -rw-r--r--
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'''
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']
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