Python Tutorial Part 5 — Loops (for & while)

Python Full Tutorial — Part 5

Real programs repeat work. Writing the same code again and again is stupidity. Loops solve this.

What is a Loop?

A loop runs the same block of code multiple times until a condition is met.

The `for` Loop

for loop is used when you know how many times something should run.

Basic for Loop


for i in range(5):
    print(i)

Output:
0 1 2 3 4

Understanding `range()`

range(start, stop)


for i in range(1, 6):
    print(i)

Starts from 1, stops before 6.

Looping Through Strings

String Loop


name = "Python"

for ch in name:
    print(ch)

The `while` Loop

while loop runs as long as condition is True.

Basic while Loop


count = 1

while count <= 5:
    print(count)
    count += 1

Infinite Loop (Danger)

If condition never becomes False, loop never stops.

Infinite Loop Example


while True:
    print("This will run forever")

The `break` Statement

break stops the loop immediately.

Using break


for i in range(1, 10):
    if i == 5:
        break
    print(i)

The `continue` Statement

continue skips current iteration.

Using continue


for i in range(1, 6):
    if i == 3:
        continue
    print(i)

Real-World Example

Password Attempts


attempts = 0

while attempts < 3:
    password = input("Enter password: ")

    if password == "python123":
        print("Access granted")
        break
    else:
        print("Wrong password")

    attempts += 1

Common Beginner Mistakes

Forgetting to update loop variable
Infinite loops by mistake
Wrong indentation

Key Takeaway

If you understand loops, you understand automation. This is how software scales.

Next part: Data Structures — List, Tuple, Set, Dictionary.