Compare if two variables reference the same object in python

Question

How to check whether two variables reference the same object?

x = [\'a\', \'b\', \'c\']
y = x                 # x and y reference the same object
z = [\'a\', \'b         


        

Answer 1

While the two correct solutions x is z and id(x) == id(z) have already been posted, I want to point out an implementation detail of python. Python stores integers as objects, as an optimization it generates a bunch of small integers at its start (-5 to 256) and points EVERY variable holding an integer with a small value to these preinitialized objects. More Info

This means that for integer objects initialized to the same small numbers (-5 to 256) checking if two objects are the same will return true (ON C-Pyhon, as far as I am aware this is an implementation detail), while for larger numbers this only returns true if one object is initialized form the other.

> i = 13
> j = 13
> i is j
True

> a = 280
> b = 280
> a is b
False

> a = b
> a
280
> a is b
True