Python range in for Loop

Introduction

The range() function in Python is used to generate a sequence of numbers. It is often used with the for loop to execute a block of code a specific number of times. The range() function is highly versatile and allows for efficient iteration over a sequence of numbers.

Syntax

The range() function has three different ways to be called:

1. range(stop): Generates numbers from 0 to stop - 1.
2. range(start, stop): Generates numbers from start to stop - 1.
3. range(start, stop, step): Generates numbers from start to stop - 1, with a specified step.

Example

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

Output:

0
1
2
3
4

Using range(stop)

Generates numbers from 0 to stop - 1.

Example

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

Output:

0
1
2
3
4

Using range(start, stop)

Generates numbers from start to stop - 1.

Example

for i in range(2, 7):
    print(i)

Output:

2
3
4
5
6

Using range(start, stop, step)

Generates numbers from start to stop - 1, with a specified step.

Example

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

Output:

1
3
5
7
9

Using break in a for Loop with range()

The break statement is used to exit the loop prematurely, regardless of the loop condition.

Example

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

Output:

0
1
2
3
4

Using continue in a for Loop with range()

The continue statement skips the current iteration and proceeds to the next iteration of the loop.

Example

for i in range(10):
    if i % 2 == 0:
        continue
    print(i)

Output:

1
3
5
7
9

Iterating Over a String Using range()

A for loop can be used to iterate over the indices of a string using the range() function.

Example

text = "Hello"
for i in range(len(text)):
    print(text[i])

Output:

H
e
l
l
o

Simple Programs Using range() in for Loop

Program 1: Sum of First N Natural Numbers

This program calculates the sum of the first n natural numbers.

n = 10
sum = 0

for i in range(1, n + 1):
    sum += i

print(f"The sum of the first {n} natural numbers is {sum}")

Output:

The sum of the first 10 natural numbers is 55

Program 2: Factorial of a Number

This program calculates the factorial of a given number.

num = 5
factorial = 1

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

print(f"The factorial of {num} is {factorial}")

Output:

The factorial of 5 is 120

Program 3: Print Each Character of a String

This program prints each character of a given string using the range() function.

text = "Hello, World!"

for i in range(len(text)):
    print(text[i])

Output:

H
e
l
l
o
,

W
o
r
l
d
!

Program 4: Iterate Over a List of Numbers and Print Their Squares

This program iterates over a list of numbers and prints their squares.

numbers = [1, 2, 3, 4, 5]

for i in range(len(numbers)):
    print(f"The square of {numbers[i]} is {numbers[i]**2}")

Output:

The square of 1 is 1
The square of 2 is 4
The square of 3 is 9
The square of 4 is 16
The square of 5 is 25

Program 5: Print Even Numbers from 1 to 10

This program prints all the even numbers from 1 to 10 using the range() function.

for i in range(1, 11):
    if i % 2 == 0:
        print(f"{i} is an even number")

Output:

2 is an even number
4 is an even number
6 is an even number
8 is an even number
10 is an even number

Conclusion

The range() function is used for generating sequences of numbers in Python, making it especially useful for for loops. By understanding how to use range() with different parameters (stop, start, stop, and start, stop, step), you can create efficient and flexible loops to iterate over a wide variety of sequences. The provided examples and programs demonstrate practical applications of the range() function in solving common programming tasks.