Loops in Python are used to execute a block of code repeatedly. Python provides two types of loops:

1. for Loop – Used for iterating over sequences like lists, tuples, and strings.
2. while Loop – Executes as long as a condition remains True.

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1. The for Loop

The for loop is used to iterate over sequences (lists, tuples, dictionaries, strings, etc.).

Syntax:

for variable in sequence:
    # Code to execute

Example 1: Looping through a List

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

Output:

apple
banana
cherry

Example 2: Looping through a String

word = "Python"
for letter in word:
    print(letter)

Output:

P
y
t
h
o
n

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Using range() in a for Loop

The range() function generates a sequence of numbers and is commonly used in loops.

Example 3: Looping with range()

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

Output:

0
1
2
3
4

• range(5) generates numbers from 0 to 4 (excluding 5).

Example 4: Using range(start, stop, step)

for i in range(1, 10, 2):
    print(i)

Output:

1
3
5
7
9

• range(1, 10, 2) starts from 1, increments by 2, and stops before 10.

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Looping through a Dictionary

student = {"name": "John", "age": 20, "grade": "A"}
for key, value in student.items():
    print(key, ":", value)

Output:

name : John
age : 20
grade : A

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Nested for Loops

A for loop inside another for loop is called a nested loop.

for i in range(1, 4):
    for j in range(1, 3):
        print(f"i={i}, j={j}")

Output:

i=1, j=1
i=1, j=2
i=2, j=1
i=2, j=2
i=3, j=1
i=3, j=2

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2. The while Loop

A while loop runs as long as a given condition is True.

Syntax:

while condition:
    # Code to execute

Example 1: Simple while Loop

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

Output:

1
2
3
4
5

• The loop runs until count exceeds 5.

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Using break and continue in Loops

1. break Statement (Stops the loop immediately)

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

Output:

1
2
3
4

• The loop stops when num reaches 5.

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2. continue Statement (Skips the current iteration and continues)

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

Output:

1
2
4
5

• 3 is skipped due to continue.

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Using else with Loops

Python allows an else clause with both for and while loops. The else block executes when the loop finishes normally (without break).

Example 1: else with for

for num in range(1, 4):
    print(num)
else:
    print("Loop finished.")

Output:

1
2
3
Loop finished.

Example 2: else with while

x = 1
while x < 4:
    print(x)
    x += 1
else:
    print("While loop finished.")

Output:

1
2
3
While loop finished.

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Nested while Loops

i = 1
while i <= 2:
    j = 1
    while j <= 3:
        print(f"i={i}, j={j}")
        j += 1
    i += 1

Output:

i=1, j=1
i=1, j=2
i=1, j=3
i=2, j=1
i=2, j=2
i=2, j=3