Python Program to Print All Prime Numbers in an Interval

Introduction

Printing all prime numbers within a specific interval is a common task in programming. This tutorial will guide you through creating a Python program that finds and prints all prime numbers within a given range.

Problem Statement

Create a Python program that:

• Takes two numbers as input, representing the lower and upper bounds of an interval.
• Finds and prints all prime numbers within this interval.

Example:

• Input: start = 10, end = 50
• Output: Prime numbers between 10 and 50 are: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47

Solution Steps

1. Take Input for the Interval: Use the input() function to get the lower and upper bounds from the user.
2. Convert Input to Integers: Convert the input strings to integers using int().
3. Check Each Number in the Interval: For each number in the range, check if it is prime.
4. Display the Prime Numbers: Collect and display all prime numbers found within the interval.

Python Program

# Python Program to Print All Prime Numbers in an Interval
# Author: https://www.rameshfadatare.com/

import math

# Step 1: Take input for the interval
start = int(input("Enter the start of the interval: "))
end = int(input("Enter the end of the interval: "))

# Step 2: Check each number in the interval
print(f"Prime numbers between {start} and {end} are:")
for num in range(start, end + 1):
    if num > 1:  # Prime numbers are greater than 1
        is_prime = True
        for i in range(2, int(math.sqrt(num)) + 1):
            if num % i == 0:
                is_prime = False
                break
        if is_prime:
            print(num, end=" ")
print()  # For a newline after printing all prime numbers

Explanation

Step 1: Take Input for the Interval

• The input() function prompts the user to enter the start and end of the interval. The inputs are converted to integers using int().

Step 2: Check Each Number in the Interval

• The program iterates over each number in the specified range. For each number greater than 1, it checks if the number is divisible by any number from 2 to the square root of that number. If no divisors are found, the number is prime.

Step 3: Display the Prime Numbers

• The print() function is used to display all prime numbers found within the interval. The numbers are printed on the same line, separated by spaces.

Output Example

Example:

Enter the start of the interval: 10
Enter the end of the interval: 50
Prime numbers between 10 and 50 are:
11 13 17 19 23 29 31 37 41 43 47 

Example:

Enter the start of the interval: 5
Enter the end of the interval: 20
Prime numbers between 5 and 20 are:
5 7 11 13 17 19 

Conclusion

This Python program demonstrates how to find and print all prime numbers within a specified interval. It effectively combines loops, conditionals, and mathematical concepts, making it a valuable example for beginners learning about prime numbers and control structures in Python.