[Python-Dev] misbehaving contains (original) (raw)

Steven Bethard steven.bethard at gmail.com
Wed Jan 23 02:03:57 CET 2008

On Jan 22, 2008 5:40 PM, Raymond Hettinger <python at rcn.com> wrote:

[Daniel Stutzbach] > There are many places in the C implementation where a slot > returns an int rather than a PyObject. There other replies > in this thread seem to support altering the signature of the > slot to return a PyObject. Is this setting a precedent that > all slots should return a PyObject?

I hope not. [snip] And, would we lose the nice relationship expressed by: for elem in container: assert elem in container

We've already lost this if anyone really wants to break it::

>>> class C(object):
...     def __iter__(self):
...         return iter(xrange(3))
...     def __contains__(self, item):
...         return False
...
>>> c = C()
>>> for item in c:
...     print item in c
...
False
False
False

Of course, anyone who decides to break their container classes in that way is asking for trouble. ;-)

STeVe

I'm not in-sane. Indeed, I am so far out of sane that you appear a tiny blip on the distant coast of sanity. --- Bucky Katt, Get Fuzzy

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