python-features

How For Loops Compile

What machine code Pyvorin generates for Python for loops.

Published May 30, 2026

Range Loops

for i in range(n) compiles to a simple counted loop in machine code.

for x in data uses fast iteration protocol with inline cache.

for i, x in enumerate(data) maintains index counter in a register.

for a, b in zip(list1, list2) iterates both lists in parallel.