Mainly, the call to range() has to construct something that it returns, that means allocating memory, which is probably going to dwarf any other code involved i

Mainly, the call to range() has to construct something that it returns, that means allocating memory, which is probably going to dwarf any other code involved in this. (In case of range(1,5) I tend to assume that constructing [1,2,3,4] is probably marginally faster than constructing rangeobject) Also, as noted in other comments, range object has special cased O(1) implementation of in for integers (range_contains_long() in Objects/rangeobject.c) CPython bytecode interpreter tries to minimize amount of branching it causes by using some non-obvious tricks, but still by definition it is going to cause at least one essentially unpredictable branch per interpreted instruction, so optimizing for number of branches in user python code is mostly pointless endeavor.