[Python-Dev] _length_cue()

Armin Rigo arigo at tunes.org
Thu Feb 9 00:51:56 CET 2006

Hi Raymond,

On Wed, Feb 08, 2006 at 03:02:21PM -0500, Raymond Hettinger wrote:
> IMHO, the "safety reasons" are imaginary -- the scenario would involve 
> subclassing one of these builtin objects and attaching an identically named 
> private method.

No, the senario applies to any user-defined iterator class, not
necessary subclassing an existing one:

>>> class MyIter(object):
...     def __iter__(self):
...         return self
...     def next(self):
...         return whatever
...     def _length_cue(self):
...         print "oups! please, CPython, don't call me unexpectedly"
>>> list(MyIter())
oups! please, CPython, don't call me unexpectedly

This means that _length_cue() is at the moment a special method, in the
sense that Python can invoke it implicitely.

This said, do we vote for __length_hint__ or __length_cue__? :-)
And does anyone objects about __getitem_hint__ or __getitem_cue__?
Maybe __lookahead_hint__ or __lookahead_cue__?


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