sameness/identity

Markus Schaber markus at schabi.de
Mon Oct 1 10:44:14 CEST 2001


Hi,

chajadan <python at chajadan.net> schrub:

> I've been watching this thread, and I'm a little confused as to the
> momentum.
> 
> As I see it, there are only two qualities of 'sameness': equality and
> identity.
> 
> 1 + 2 = 3
> 
> 1 plus 2 equals 3
> 1 plus 2 is not 3
> 
> Equals just means holds the same value. But nothing can be something
> else. Just equal to it.
> 
> If you say 3 is 3, in the sense that there is only one 3 in existance,
> then you are right.
> 
> If you add a level of abstraction, and say x = 3 and y = 3, now is
> that 3 and the other 3 the same?

Yes. But x and y are different names.

Just to confuse you some more:

>>> a = 3
>>> b = 3
>>> a is b
1
>>> a = 10000
>>> b = 10000
>>> a is b
0

Identity of python numbers is an implementation detail. For most uses 
(concerning numbers), I would recommend to use ==.
 
markus

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"The strength of the Constitution lies entirely in the determination of 
each citizen to defend it. Only if every single citizen feels duty 
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