Python Loops

Loops

Loops help us repeat actions in Python. Imagine telling the computer: "Do this again and again." That’s what loops are for!

Why Use Loops?

Let’s say you want to print "Hi!" five times. Without a loop, you’d write:

print("Hi!")
print("Hi!")
print("Hi!")
print("Hi!")
print("Hi!")

That works… but what if you wanted to print it 100 times? That’s where loops save time.

Types of Loops in Python

• for loop – repeats a certain number of times
• while loop – repeats while a condition is true

1. for Loop

A for loop is useful when you know in advance how many times you want to repeat a block of code. It’s commonly used to iterate over sequences like lists, strings, or ranges of numbers.

Syntax

for variable in sequence:
    # code to run for each item in the sequence

• for: The loop keyword that starts the iteration.
• variable: A temporary variable that takes the value of each item in the sequence, one at a time.
• in: A keyword that links the loop variable with the sequence to iterate over.
• sequence: Any iterable object like range(), a list, or a string.
• Indented block: The code under the loop that will execute once per iteration.

Example

for i in range(5):
    print("Hi!")

Hi!
Hi!
Hi!
Hi!
Hi!

Explanation:

• range(5) generates a sequence of numbers from 0 to 4 (5 numbers in total).
• The variable i takes on each of those values — first 0, then 1, and so on up to 4.
• For each value of i, the line print("Hi!") is executed once.
• As a result, "Hi!" is printed 5 times.

2. while Loop

A while loop in Python is used to repeatedly execute a block of code as long as a specified condition remains True.

Syntax

while condition:
    # code to repeat

• while: The keyword that starts the loop.
• condition: An expression that is evaluated before each iteration. The loop runs as long as this condition is True.
• :: Indicates the start of the loop block.
• Indented block: The code inside the loop that gets executed repeatedly.

Example

count = 1
while count <= 3:
    print("Welcome!")
    count = count + 1

Explanation:

• count is initialized to 1.
• The condition count <= 3 is checked before each iteration.
• If the condition is True, the loop body runs — printing "Welcome!" and then increasing count by 1.
• This continues for count = 1, 2, and 3.
• When count becomes 4, the condition count <= 3 becomes False, so the loop stops.

Looping Through a List

A for loop in Python can be used to iterate over elements in a list — executing a block of code once for each item.

Example

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

apple
banana
cherry

Explanation:

• A list named fruits is defined with three string elements: "apple", "banana", and "cherry".
• The for loop goes through each element in the list one by one.
• On each iteration, the variable fruit holds the current list item.
• The statement prints the current value of fruit.
• As a result, each fruit name is printed on a new line.

Using break in a Loop

break stops the loop early.

for i in range(5):
    if i == 3:
        break
    print(i)

Explanation:

• When i becomes 3, the break line runs and stops the loop.
• So 3 and 4 are never printed.

Using continue in a Loop

continue skips the rest of the loop for that time only.

for i in range(5):
    if i == 2:
        continue
    print(i)

Explanation:

• When i is 2, it skips print(i).
• Everything else runs normally.