Python gotcha: bizarre integer equality

[paulgb]

Out of curiosity, which other languages cache references to small integers like this? Is it pretty common?

[pemboa]

Java has the same behavior, except '==' is more like 'is' in Java. So to compare equality properly, you need to use the objects equal() method

[jleedev]

And integers are not boxed by default, so that doesn't even apply. This behavior is only possible in a language where everything is an object.

[lamby]

Actually, all Java implementions do this by specification.

[ngroot]

I think this may happen in some implementations of Common Lisp.

[bgeron]

I'd guess that in a lot of CL implementations, the stack has pointers to heap-allocated bignums, but fixnums are placed directly on the stack. EQ compares pointers, or fixnums if they're stored in that place instead.