Reverse Iteration

Iterating backwards through sequences is often necessary for algorithms that build results from end to beginning, or when modifications affect indices of later elements. Python provides several ways to iterate in reverse. The reversed() Function range() with Negative Step Why Reverse Iteration Reverse iteration is essential when modifying a list based on indices. Deleting from the beginning shifts all later indices, but deleting from the end keeps earlier indices valid: This code tries to remove even numbers while iterating forward, but a stale index causes it to skip elements. Fix the loop direction so that every even number is removed safely. Building Results Backwards Some algorithms naturally build results from end to beginning. Reverse iteration aligns the logic with the output order: