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Python Programs - Functions

Function to generate a list of prime numbers in a range - Python Program

Example 1 :

Python 
def primes_in_range(start, end):
    """Return primes between start and end."""
    primes = []
    for num in range(start, end+1):
        if num > 1:
            for i in range(2, int(num**0.5)+1):
                if num % i == 0:
                    break
            else:
                primes.append(num)
    return primes

print(primes_in_range(10, 30))

Output

 
OUTPUT  :
[11, 13, 17, 19, 23, 29]

Example 2 : Advanced Program

Python 
import math

def is_prime(num):
    """
    Checks if a given number is prime.

    Args:
        num (int): The number to check.

    Returns:
        bool: True if the number is prime, False otherwise.
    """
    if num <= 1:
        return False  # Numbers less than or equal to 1 are not prime
    for i in range(2, int(math.sqrt(num)) + 1):
        if num % i == 0:
            return False  # If divisible by any number, it's not prime
    return True  # If no divisors found, it's prime

def generate_primes_in_range(start, end):
    """
    Generates a list of prime numbers within a specified range (inclusive).

    Args:
        start (int): The lower bound of the range.
        end (int): The upper bound of the range.

    Returns:
        list: A list containing prime numbers within the given range.
    """
    prime_numbers = []
    for number in range(start, end + 1):
        if is_prime(number):
            prime_numbers.append(number)
    return prime_numbers

# Example Usage and Output:
lower_bound = 10
upper_bound = 50
primes = generate_primes_in_range(lower_bound, upper_bound)
print(f"Prime numbers between {lower_bound} and {upper_bound}: {primes}")

Output

 
OUTPUT  :
Prime numbers between 10 and 50: [11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]

Explanation:

is_prime(num) function:

  • This helper function takes an integer numas input.
  • It first handles edge cases: numbers less than or equal to 1 are not prime, so it returns False.
  • It then iterates from 2 up to the square root of num(inclusive). This optimization is based on the fact that if a number num has a divisor greater than its square root, it must also have a divisor smaller than its square root.
  • If numis divisible by any number in this range, it is not prime, and the function returns False.
  • If the loop completes without finding any divisors, numis prime, and the function returns True.

 

generate_primes_in_range(start, end) function:

  • This function takes startand end integers defining the range.
  • It initializes an empty list called prime_numbers.
  • It iterates through each numberin the specified range (from start to end, inclusive).
  • For each number, it calls the is_prime()function to check if it's prime.
  • If is_prime()returns True, the number is appended to the prime_numbers
  • Finally, the function returns the prime_numbers
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