Integer identity caching

Question

Accepted Answer

CPython caches small integer objects in the range -5 to 256, so a and b are the exact same object in memory. Integers outside that range are not cached, so c and d are two separate objects with the same value - 'is' tests identity, not equality. The takeaway: always use == to compare values; 'is' is for identity checks like 'x is None'. Relying on integer identity caching is an implementation detail, not a language guarantee.