The for Loop and range()

A for loop in Python repeats a block of code once for every item in a sequence — a list, a string, or a range of numbers. Python has no traditional C-style for loop with a counter, condition, and increment all in one line; instead, it always iterates directly over a sequence of values.

Iterating Over a Sequence Directly

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)
# apple
# banana
# cherry

This is effectively what other languages call a "for-each" loop — Python does not have a separate keyword for it, because the regular for loop already works this way by default.

The range() Function

When you need to repeat something a fixed number of times rather than iterating over an existing collection, range() generates a sequence of numbers on demand.

for i in range(5):
    print(i)
# 0 1 2 3 4 — start is inclusive (0), stop is EXCLUSIVE (5)

The stop value is always exclusive — range(0, 10) produces 10 numbers (0 through 9), never including 10 itself. This is consistent with how string and list slicing behave too.

Counting Backward

for i in range(10, 0, -1):
    print(i)
# Counts down: 10, 9, 8, ... 1

Iterating Over a String

word = "Python"
for letter in word:
    print(letter)
# P y t h o n — printed one character per line

Using enumerate() to Get the Index Too

When you need both the position and the value while looping, enumerate() is the idiomatic Python way — far cleaner than manually tracking an index variable.

fruits = ["apple", "banana", "cherry"]

for index, fruit in enumerate(fruits):
    print(index, fruit)
# 0 apple
# 1 banana
# 2 cherry

Looping with an Index the "Old" Way (and Why to Avoid It)

# Works, but not idiomatic Python
fruits = ["apple", "banana", "cherry"]
for i in range(len(fruits)):
    print(fruits[i])

# Preferred — direct iteration, cleaner and less error-prone
for fruit in fruits:
    print(fruit)

The for-else Clause — Unique to Python

A for loop can have an else block that runs only if the loop completed without hitting a break — useful for "search and report not found" logic.

numbers = [4, 8, 15, 16]

for n in numbers:
    if n == 7:
        print("Found 7!")
        break
else:
    print("7 was not found in the list")
# Output: 7 was not found in the list

Interview tip: A common question is "Why doesn't Python have a do-while loop?" — Python deliberately omits it; the same effect is achieved with a while True loop combined with a break condition checked inside the loop body, which is considered more readable in Python's philosophy.