Loops

Python's for loop is not a counter loop. It walks over an iterable, binding each item to the loop variable in turn. The iterable can be a list, a string, a dict, a file object, a range, or any object that defines an iterator.

range(start, stop, step) is the closest thing to the C-style counter. It produces an iterator that yields integers in the requested range. For most purposes you write for i in range(n): and read it as "do this n times".

If you find yourself reaching for an index just to read both the index and the value, use enumerate(items). It yields (i, item) pairs and is more idiomatic than tracking an integer manually.

for i in range(3):
    print(i)             # 0, 1, 2

for i, name in enumerate(["a", "b"]):
    print(i, name)       # 0 a, then 1 b