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Groups > comp.lang.python > #42823

is operator versus id() function

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Until now, I was quite sure that the is operator acts the same as the id builtin function, or, to be more formal, that o1 is o2 to be exactly equivalent to id(o1) == id(o2). This equivalence is reported in many books, for instance Martelli's Python in a Nutshell.

But with the following code, I'm not still sure the equivalence above is correct. Here's the code :


#--------------------------------------------------------
class A(object):
    def f(self):
        print "A"

a=A()
print id(A.f) == id(a.f), A.f is a.f
#--------------------------------------------------------


outputing:

True False

So, could someone please explain what exactly the is operator returns ? The official doc says :

The ‘is‘ operator compares the identity of two objects; the id() function returns an integer representing its identity (currently implemented as its address).

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is operator versus id() function Candide Dandide <c.candide@laposte.net> - 2013-04-05 06:49 -0700
  Re: is operator versus id() function Arnaud Delobelle <arnodel@gmail.com> - 2013-04-05 15:53 +0100
    Re: is operator versus id() function candide <c.candide@laposte.net> - 2013-04-05 09:40 -0700
      Re: is operator versus id() function Tim Delaney <timothy.c.delaney@gmail.com> - 2013-04-06 06:57 +1100
    Re: is operator versus id() function candide <c.candide@laposte.net> - 2013-04-05 09:40 -0700
  Re: is operator versus id() function Nobody <nobody@nowhere.com> - 2013-04-06 14:35 +0100

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