Python for Loop

The for loop in Python is used to repeat a block of code for each item in a sequence or other iterable object. It is commonly used with lists, tuples, strings, dictionaries, sets and the range() function.

Unlike a traditional counter-controlled loop, a Python for loop directly accesses each item of the iterable.

Syntax of for Loop

for variable in iterable:
    statement

The loop variable takes each value from the iterable one by one and executes the indented statements for every value.

Simple for Loop

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

0
1
2
3
4

The range(5) function generates values from 0 to 4.

for Loop with a List

fruits = ["Apple", "Banana", "Mango"]

for fruit in fruits:
    print(fruit)

Apple
Banana
Mango

The loop accesses each element of the list one at a time.

for Loop with a Tuple

numbers = (10, 20, 30, 40)

for number in numbers:
    print(number)

10
20
30
40

for Loop with a String

A string is an iterable sequence of characters. Therefore, a for loop can be used to process each character separately.

word = "Python"

for ch in word:
    print(ch)

P
y
t
h
o
n

for Loop with range()

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

1
2
3
4
5

Here, the starting value is 1 and the stopping value is 6. The stopping value is not included.

for Loop with Start and Stop Values

for i in range(5, 10):
    print(i)

5
6
7
8
9

for Loop with Step Value

for i in range(2, 11, 2):
    print(i)

2
4
6
8
10

The third argument of range() specifies the step size. Here, the value increases by 2 after every iteration.

Reverse for Loop

for i in range(5, 0, -1):
    print(i)

5
4
3
2
1

Printing Even Numbers

for i in range(2, 11, 2):
    print(i)

2
4
6
8
10

Printing Odd Numbers

for i in range(1, 11, 2):
    print(i)

1
3
5
7
9

Calculating Sum using for Loop

numbers = [10, 20, 30, 40, 50]
total = 0

for number in numbers:
    total = total + number

print("Sum =", total)

Sum = 150

Finding the Largest Number

numbers = [12, 45, 23, 67, 34]

largest = numbers[0]

for number in numbers:
    if number > largest:
        largest = number

print("Largest =", largest)

Largest = 67

Counting Elements using for Loop

numbers = [10, 20, 30, 40, 50]
count = 0

for number in numbers:
    count = count + 1

print("Number of elements =", count)

Number of elements = 5

for Loop with if Statement

A for loop can contain an if statement to perform conditional processing during each iteration.

numbers = [10, 15, 20, 25, 30]

for number in numbers:
    if number % 2 == 0:
        print(number)

10
20
30

for Loop with else

Python allows an else block to be associated with a for loop. The else block executes when the loop completes normally.

for i in range(5):
    print(i)
else:
    print("Loop completed")

0
1
2
3
4
Loop completed

Nested for Loop

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

for i in range(1, 4):
    for j in range(1, 4):
        print(i, j)

1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3

Multiplication Table using for Loop

number = 5

for i in range(1, 11):
    print(number, "x", i, "=", number * i)

5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50

Using break in for Loop

The break statement terminates the loop immediately.

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

1
2
3
4

Using continue in for Loop

The continue statement skips the current iteration and moves to the next iteration.

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

1
2
4
5

Using pass in for Loop

The pass statement does nothing. It can be used as a placeholder where a statement is syntactically required.

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

0
1
2
3
4

Practical Example: Factorial using for Loop

number = 5
factorial = 1

for i in range(1, number + 1):
    factorial = factorial * i

print("Factorial =", factorial)

Factorial = 120

Practical Example: Count Vowels

text = "Python Programming"
count = 0

for ch in text.lower():
    if ch in "aeiou":
        count = count + 1

print("Number of vowels =", count)

Number of vowels = 4

Practical Example: Reverse a String

text = "Python"
reverse_text = ""

for ch in text:
    reverse_text = ch + reverse_text

print(reverse_text)

nohtyP

Practical Example: Pattern using for Loop

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

*
**
***
****
*****

for Loop with Dictionary

student = {
    "name": "Rahul",
    "age": 20,
    "marks": 85
}

for key in student:
    print(key, ":", student[key])

name : Rahul
age : 20
marks : 85

for Loop with Dictionary Items

student = {
    "name": "Rahul",
    "marks": 85
}

for key, value in student.items():
    print(key, ":", value)

name : Rahul
marks : 85

for Loop with Set

numbers = {10, 20, 30}

for number in numbers:
    print(number)

A set is unordered, so the order in which its elements are displayed should not be assumed.

Important Points

• The for loop is used to iterate over an iterable.
• Lists, tuples, strings, dictionaries, sets and ranges can be used with a for loop.
• The loop variable receives one item at a time.
• Indentation defines the body of the loop.
• The range() function is commonly used with for loops.
• break terminates the loop.
• continue skips the current iteration.
• pass acts as a placeholder.
• A for loop can contain an if statement.
• Python also supports nested for loops.