Why does id({}) == id({}) and id([]) == id([]) in CPython?

Question

Why does CPython (no clue about other Python implementations) have the following behavior?

tuple1 = ()
tuple2 = ()                                                    


        

Answer 1

CPython is garbage collecting objects as soon as they go out of scope, so the second [] is created after the first [] is collected. So, most of the time it ends up in the same memory location.

This shows what's happening very clearly (the output is likely to be different in other implementations of Python):

class A(object):
    def __init__(self): print "a",
    def __del__(self): print "b",

# a a b b False
print A() is A()
# a b a b True
print id(A()) == id(A())