Python: object identity question?

Question

Possible Duplicate:
Python “is” operator behaves unexpectedly with integers

>>>a=123
>>>b=123
>>>a is b
True
>>>id(a)==id(b)
True

My question is, why is id(a) the same as id(b)?.
Aren't they two different instances of class int?

Not exact dupe.. But that question is more clear and useful.. Thanx — asdfg, Mar 10 '10 at 19:14
The following was even more surprising to me: x = "helloworld"; y = "hello" + "world"; x is y — Federico A. Ramponi, Mar 10 '10 at 21:04

score 3 · Answer 1 · answered Mar 10 '10 at 19:05

3

Usually small integers reference the same cached object in memory for efficiency purposes.

answered Mar 10 '10 at 19:05

jackbot

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score 2 · Answer 2 · answered Mar 10 '10 at 19:05

2

ints are cached. That is an implementation detail that shouldn't matter since ints are immutable anyway.

answered Mar 10 '10 at 19:05

nosklo

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score 1 · Answer 3 · edited Sep 27 '12 at 16:19

1

variables

a and b

both are references to the object 123 whose id is unique.

when u assign same value 123 to two diff variables a and b,

then same object 123 is assigned to both variables a and b but reference count made to that object increases in your case refrecnce count for object 123 is two

edited Sep 27 '12 at 16:19

m1k3y3

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answered Aug 03 '12 at 11:53

Pankaj Moolrajani

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Python: object identity question?

3 Answers3