for-loops.md

Python by Example: For Loops

A for loop repeats code for each item in a sequence. Unlike C or Java, Python's for iterates over collections directly—you rarely need an index variable. Use range() when you need a sequence of numbers. For loops are one of the most common constructs in Python.

What you'll learn:

• Looping over lists and other sequences
• Using range() for numeric loops
• range(start, stop, step)—stop is exclusive

# Loop over a list
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

# Loop with range(start, stop) — stop is exclusive
for i in range(3):
    print(i)

# range with start and end
for i in range(2, 5):
    print(i)

# range with step
for i in range(0, 10, 2):
    print(i)

range(3) produces 0, 1, 2—not 3. The end value is always exclusive. range(0, 10, 2) goes 0, 2, 4, 6, 8.

To run this program:

$ python source/for-loops.py
apple
banana
cherry
0
1
2
2
3
4
0
2
4
6
8

Tip: Prefer for item in items: over for i in range(len(items)): when you don't need the index. It's clearer and less error-prone.

Try it: Loop over a string—each character is an item.

Source: for-loops.py

Next: While Loops