Good info about Python, but you are incorrect about Ruby. Hashes and arrays are totally different in the Ruby implementations I know of. EDIT: Sorry, I misread

Good info about Python, but you are incorrect about Ruby. Hashes and arrays are totally different in the Ruby implementations I know of. EDIT: Sorry, I misread you. Ruby MRI and CPython are indeed similar. At least in Ruby MRI (the mainline) arrays are implemented as a struct with a size and a pointer to a normal C array which contains the object references (references in MRI are pointers to object structs which use the lower bits to inline integers of <= 31 or 63 bits, true, false, nil and symbols). Hashes in MRI I have not looked that much into but I believe they are a hash tables which in ruby 1.9 retain insertion order using pointers like a singly linked list.