Python for Loop Explained — Syntax, Examples and Common Mistakes

Every real program does repetitive work. A weather app checks temperatures for 365 days. A music app loads every song in your library. An online store applies a discount to every item in your cart. Without a way to repeat actions automatically, you'd have to write the same line of code hundreds of times — which is not just tedious, it's fragile. Change one thing and you'd have to update every single copy.

What a for Loop Actually Does — The Core Idea

A for loop says: 'take this collection of things, visit each one in order, and run the same block of code for each.' Python handles all the counting and moving-forward for you. You just describe what to DO on each visit.

The collection you loop over can be a list of names, a string of characters, a range of numbers — almost anything that holds multiple items. Python calls these 'iterables', but you can think of them as 'anything you can step through one piece at a time.'

The basic shape of a for loop is always the same: the word for, then a variable name you choose (this is your 'current item' holder), then in, then the collection, then a colon. Everything indented below that runs once per item. The indentation is not optional — Python uses it to know which lines belong inside the loop.

# A simple list of planet names
planets = ["Mercury", "Venus", "Earth", "Mars", "Jupiter"]

# for loop: visit each planet one at a time
for planet in planets:          # 'planet' holds the current item each round
    print(f"Visiting {planet}") # this line runs once per planet

# This line is NOT indented, so it runs AFTER the loop finishes
print("Tour of the solar system complete!")

Looping Over Numbers with range() — Your Most-Used Tool

Most beginners need to repeat something a set number of times — run a countdown from 10, process 100 items, print a multiplication table. For that, Python gives you range(). It generates a sequence of numbers on demand without storing them all in memory.

range(5) gives you 0, 1, 2, 3, 4 — five numbers starting at zero. This trips up almost every beginner: range counts from zero by default, and the number you pass in is NOT included. Think of it as 'up to but not including 5.'

range(start, stop) lets you control where counting begins. range(1, 6) gives 1, 2, 3, 4, 5. range(start, stop, step) adds a step — range(0, 10, 2) gives you every even number from 0 to 8. You can even count backwards with a negative step: range(5, 0, -1) counts down from 5 to 1.

# --- Example 1: Basic range, repeat 5 times ---
print("=== Countdown prep ===")
for step_number in range(5):          # generates 0, 1, 2, 3, 4
    print(f"Step {step_number}")

# --- Example 2: range with start and stop ---
print("\n=== Lap counter ===")
for lap in range(1, 6):               # generates 1, 2, 3, 4, 5 (NOT 6)
    print(f"Lap {lap} complete")

# --- Example 3: range with a step (every 2nd number) ---
print("\n=== Even floors only ===")
for floor in range(0, 11, 2):         # 0, 2, 4, 6, 8, 10
    print(f"Elevator stops at floor {floor}")

# --- Example 4: counting backwards ---
print("\n=== Rocket launch ===")
for countdown in range(5, 0, -1):     # 5, 4, 3, 2, 1
    print(f"T-minus {countdown}...")
print("Liftoff!")

Looping Over Strings, Dictionaries, and Using enumerate()

A string in Python is just a sequence of characters, and you can loop over it the same way you loop over a list. Python will hand you one character at a time. This is surprisingly useful for tasks like counting vowels, reversing text, or scanning for special characters.

Dictionaries are a bit different. When you loop over a dictionary directly, you get its keys. To get both keys and values together, use .items() — it hands you both as a pair each round.

Here's a power move: enumerate(). Often you need both the item AND its position number. Without enumerate, beginners create a separate counter variable and increment it manually — messy and error-prone. enumerate(collection) hands you a tuple of (index, item) on each pass. You unpack it by naming two variables after for.

# --- Looping over a string ---
word = "Python"
print("=== Characters in 'Python' ===")
for character in word:               # each character, one at a time
    print(character)

# --- Looping over a dictionary ---
student_grades = {
    "Alice": 92,
    "Bob": 78,
    "Carlos": 85
}
print("\n=== Grade Report ===")
for student_name, grade in student_grades.items():  # .items() gives key AND value
    if grade >= 90:
        remark = "Excellent"
    elif grade >= 80:
        remark = "Good"
    else:
        remark = "Keep practising"
    print(f"{student_name}: {grade} — {remark}")

# --- Using enumerate() to track position ---
race_finishers = ["Aisha", "Ben", "Clara", "David"]
print("\n=== Race Results ===")
for position, runner_name in enumerate(race_finishers, start=1):  # start=1 so positions begin at 1
    print(f"Position {position}: {runner_name}")

Controlling the Loop — break, continue, and the else Clause

Sometimes you don't want to visit every single item. Maybe you're searching a list for a specific value and want to stop the moment you find it — no point checking the rest. That's break. It exits the loop immediately, as if you slammed a book shut.

continue is the opposite of a full stop — it's more of a skip. When Python hits continue, it abandons the current iteration and jumps straight to the next one. Useful when you want to process most items but ignore ones that fail a condition.

Python's for loop also has an else clause — and this genuinely surprises most people. The else block runs only if the loop completed normally, meaning it was NOT interrupted by a break. It's perfect for 'search and report' patterns: loop through items looking for something, break if found, and use else to handle the 'not found' case cleanly.

# --- break: stop the moment we find what we need ---
passenger_list = ["Tom", "Sara", "Jake", "Mia", "Leo"]
target_passenger = "Jake"

print("=== Boarding check ===")
for passenger in passenger_list:
    if passenger == target_passenger:
        print(f"Found {target_passenger}! Stopping search.")
        break                          # no point checking further
    print(f"Not {target_passenger}, checked {passenger}")

# --- continue: skip items that don't qualify ---
raw_scores = [88, -5, 76, 0, 95, -1, 60]
print("\n=== Valid scores only ===")
for score in raw_scores:
    if score <= 0:                     # invalid scores — skip them
        continue
    print(f"Recording score: {score}")

# --- for...else: only runs if loop was NOT broken out of ---
seating_chart = ["14A", "14B", "15A", "15B"]
requested_seat = "16C"

print("\n=== Seat search ===")
for seat in seating_chart:
    if seat == requested_seat:
        print(f"Seat {requested_seat} found!")
        break
else:
    # This block runs ONLY because we never hit 'break'
    print(f"Seat {requested_seat} is not available on this flight.")

Frequently Asked Questions