[EMAIL PROTECTED] wrote: > No doubt you're right but common sense dictates that membership testing > would test identity not equality. > This is one of the rare occasions where Python defeats my common sense
But object identity is almost always a fairly ill-defined concept. Consider this (Python 2.2, 'cuz that's what I have right now): Python 2.2.3 (#1, Nov 12 2004, 13:02:04) [GCC 3.2.3 20030502 (Red Hat Linux 3.2.3-42)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> al = "ab" >>> alp = al+"c" >>> alphabet = "abc" >>> al 'ab' >>> alp 'abc' >>> alphabet 'abc' >>> alp is alphabet 0 >>> alp == alphabet 1 # True on Py2.4 The only reliable thing that object identity tells you is "these two foos occupy the same memory location." Even for identical, immutable objects, this may not be true (see case above) -- some immutables do end up occupying the same memory location (try i=1;j=2;k=j-1;i is k), but this is by no means guraranteed, and indeed only happens sometimes because of optimizations. -- http://mail.python.org/mailman/listinfo/python-list
