operator module isSequenceType with builtin set produces False

[English, Mark]

X-Replace-Address:
mark.ignorethisbit.english at xxxrbccmxxx.ignorethisbittoo_and_removethosep
receding_xxxs_.com

This wasn't what I was expecting, so I thought I'd ask those more
knowledgeable, which is pretty much everybody.
Same result on Python 2.3.5 and Python 2.5.1 installed from python.org
binaries on Windows XP.

>>> try: set
>>> except NameError: from sets import Set as set
>>> class myset_fails(set): pass
>>> class myset_works(set):
>>>     def __getitem__(self): pass
>>> s = set()
>>> fails = myset_fails()
>>> works = myset_works()
>>> import operator
>>> operator.isSequenceType(s) #Not what I expected
False
>>> operator.isSequenceType(fails) #Not what I expected either
False
>>> operator.isSequenceType(works) #A hint at what isSequenceType does ?
True

Are sets not sequences ? I didn't think the isSequenceDisclaimer gave
false negatives.
See Raymond Hettinger's post here too:
http://groups.google.co.uk/group/comp.lang.python/tree/browse_frm/thread
/bd04db20cc1f23bb/36f1f48bb7be1e4b?hl=en&rnum=1&q=set+isSequenceType&_do
ne=%2Fgroup%2Fcomp.lang.python%2Fbrowse_frm%2Fthread%2Fbd04db20cc1f23bb%
2F0454f5debc01c20d%3Fhl%3Den%26lnk%3Dgst%26q%3Dset%2BisSequenceType%26#d
oc_0454f5debc01c20d

Although there are suggestions that it means simply that you're headed
in the wrong direction design wise:
http://www.mail-archive.com/python-dev@python.org/msg11576.html

but then why have isSequenceType at all ?


Not particularly vital. Just implementing __str__ on some class and if
one of the members was a sequence
I was going to format that bit of data in brackets.

Thanks,
Mark

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