python - def next() 适用于 Python pre-2.6？ (而不是 object.next 方法)

Question

Python 2.6+ 和 3.* 有 next()，但是 pre-2.6 只提供了 object.next 方法。有没有办法在 pre-2.6 中获得 next() 样式；也许是一些“def next():”结构？

Answer 1

class Throw(object): pass
throw = Throw() # easy sentinel hack
def next(iterator, default=throw):
  """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.
  """
  try:
    iternext = iterator.next.__call__
    # this way an AttributeError while executing next() isn't hidden
    # (2.6 does this too)
  except AttributeError:
    raise TypeError("%s object is not an iterator" % type(iterator).__name__)
  try:
    return iternext()
  except StopIteration:
    if default is throw:
      raise
    return default

(throw = object() 也可以工作，但这会在检查时生成更好的文档，例如 help(next)。None 不是合适，因为你必须区别对待 next(it) 和 next(it, None)。)