Python Program to Check Prime Number

Posted in Python Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 80 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the landscape of programming, dealing with prime numbers is a fundamental and interesting task. Prime numbers, those divisible only by 1 and themselves, play a crucial role in various mathematical and computational applications.

In this tutorial, we will unravel a concise yet potent Python program to determine whether a given number is a prime number.

📄 Example

Let's immerse ourselves in the Python code that executes the prime number check.

is_prime.py

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# Function to check if a number is prime
def is_prime(number):
    # 0 and 1 are not prime numbers
    if number <= 1:
        return False

    # Check for factors from 2 to the square root of the number
    for i in range(2, int(number**0.5) + 1):
        if number % i == 0:
            return False  # Found a factor, not a prime number

    return True  # No factors found, it's a prime number

# Driver program
if __name__ == "__main__":
    # Replace this value with your desired number
    test_number = 17

    # Call the function to check if the number is prime
    if is_prime(test_number):
        print(f"{test_number} is a prime number.")
    else:
        print(f"{test_number} is not a prime number.")

💻 Testing the Program

To test the program with a different number, replace the value of test_number in the if __name__ == "__main__": block.

Output

17 is a prime number.

Run the script to see whether the number is a prime number.

🧠 How the Program Works

The program defines a function is_prime that takes an integer as input and returns a boolean indicating whether the number is prime.
Inside the function, it checks if the number is less than or equal to 1; if so, it's not prime.
It then iterates through potential factors from 2 to the square root of the number.
If it finds any factor, the number is not prime; otherwise, it is prime.
The main block tests the program with a specific number (in this case, 17).

📏 Between the Given Range

Let's dive into the python code that checks and lists prime numbers in the specified range.

is_prime.py

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# Function to check if a number is prime
def is_prime(num):
    if num > 1:
        # Check for factors
        for i in range(2, int(num ** 0.5) + 1):
            if num % i == 0:
                return False
        else:
            return True
    else:
        return False

# Define the range
lower_limit = 1
upper_limit = 20

# Print prime numbers in the specified range
prime_numbers = [num for num in range(lower_limit, upper_limit + 1) if is_prime(num)]
print(f"Prime Numbers in the Range {lower_limit} to {upper_limit}:", end=" ")
print(*prime_numbers)

💻 Testing the Program

The program is set to check and list prime numbers in the range from 1 to 20. No additional input is required.

Output

Prime Numbers in the Range 1 to 20:
2 3 5 7 11 13 17 19

Run the program to see the prime numbers in the specified range.

🧠 How the Program Works

The program defines a function is_prime to check if a number is prime.
Inside the function, it iterates through the range from 2 to the square root of the number and checks for factors.
The main section defines the range (1 to 20) and prints the prime numbers in that range using list comprehension.

🧐 Understanding the Concept of Prime Numbers

Before diving into the code, let's briefly understand prime numbers.

A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers. For example, 2, 3, 5, 7, 11, and 13 are prime numbers.

🎢 Optimizing the Program

While the provided program is effective, you can explore optimizations such as using the square root of the number as the loop limit for improved efficiency.

Feel free to incorporate and modify this code as needed for your specific use case. Happy coding!