Loops in Python are used to repeat a block of code multiple times — until a specific condition becomes false.
They help reduce redundancy and automate repetitive tasks efficiently.
Example:
for i in range(5):
print("Hello, Python!")
Output:
Hello, Python! (prints 5 times)
Python mainly provides two types of loops:
for loop
while loop
Let’s understand both in detail 👇
The for loop is used when you know the number of iterations you want to perform.
Syntax:
for variable in sequence:
# code block
Example 1: Print numbers from 1 to 5
for i in range(1, 6):
print(i)
Example 2: Loop through a list
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
print(fruit)
Example 3: Loop through a string
for ch in "Python":
print(ch)
The range() function generates a sequence of numbers, often used with for loops.
| Example | Description |
|---|---|
| range(5) | 0 to 4 |
| range(1, 6) | 1 to 5 |
| range(1, 10, 2) | 1, 3, 5, 7, 9 (step = 2) |
Example:
for i in range(1, 10, 2):
print(i)
The while loop is used when you don’t know in advance how many times to repeat — it runs until a condition becomes False.
Syntax:
while condition:
# code block
Example 1: Count 1 to 5
i = 1 while i <= 5: print(i) i += 1
Example 2: Infinite loop (⚠️ avoid this!)
i = 1
while i <= 5:
print(i)
i += 1
Python provides control statements to manage loop execution — stop, skip, or hold temporarily.
| Statement | Description | Example |
|---|---|---|
| break | Stops the loop entirely | if i == 5: break |
| continue | Skips the current iteration | if i == 3: continue |
| pass | Does nothing (placeholder) | Used for empty loops or future code |
Example: break
for i in range(1, 10):
if i == 5:
break
print(i)
➡️ Stops at 4.
Example: continue
for i in range(1, 6):
if i == 3:
continue
print(i)
➡️ Skips 3, prints 1 2 4 5.
Example: pass
for i in range(3):
pass # Future code will go here
A loop inside another loop is called a nested loop.
Example:
for i in range(1, 4):
for j in range(1, 4):
print(i, j)
Output:
1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3
💡 Example 1: Sum of first n numbers
n = int(input("Enter n: "))
sum = 0
for i in range(1, n+1):
sum += i
print("Sum =", sum)
💡 Example 2: Multiplication Table
num = int(input("Enter a number: "))
for i in range(1, 11):
print(num, "x", i, "=", num*i)
💡 Example 3: Factorial using while loop
n = int(input("Enter a number: "))
fact = 1
while n > 0:
fact *= n
n -= 1
print("Factorial:", fact)
💡 Example 4: Reverse a string
word = input("Enter a word: ")
rev = ""
for ch in word:
rev = ch + rev
print("Reversed:", rev)
Print all even numbers from 1 to 50.
Find the sum of numbers divisible by 3 between 1–100.
Print the following star pattern:
*
* *
* * *
* * * *
* * * * *
Create a password system that keeps asking for input until the correct password is entered.
Generate a Fibonacci series up to n terms using a while loop.
