Prime number are positive natural number greater than 1 (N > 1) that has only two divisors i.e. 1 and itself. In other words, a prime number is a number that cannot be formed by multiplying two smaller natural numbers (except 1 and itself). For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
Example 1
def is_prime(num): if num <= 1: return False for i in range(2, int(num**0.5) + 1): if num % i == 0: return False return True def find_primes(start, end): prime_numbers = [] for num in range(start, end + 1): if is_prime(num): prime_numbers.append(num) return prime_numbers start_num = 10 end_num = 100 if start_num > end_num: print("Invalid input: Starting number cannot be greater than ending number.") else: prime_list = find_primes(start_num, end_num) if prime_list: print(f"Prime numbers between {start_num} and {end_num}:") print(prime_list) else: print(f"No prime numbers found between {start_num} and {end_num}.")
Output:
Prime numbers between 10 and 100:
[11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]
Example 2: With User Input
# function to check a number is prime or not def is_prime(num): if num <= 1: return False for i in range(2, int(num**0.5) + 1): if num % i == 0: return False return True def find_primes(start, end): prime_numbers = [] for num in range(start, end + 1): if is_prime(num): prime_numbers.append(num) return prime_numbers def get_valid_input(prompt): while True: try: value = int(input(prompt)) if value < 0: print("Please enter a positive integer.") else: return value except ValueError: print("Invalid input. Please enter a valid integer.") # Get user input for starting and ending numbers start_num = get_valid_input("Enter the starting number: ") end_num = get_valid_input("Enter the ending number: ") # Ensure start_num is less than or equal to end_num if start_num > end_num: start_num, end_num = end_num, start_num # Find and display prime numbers in the range prime_list = find_primes(start_num, end_num) if prime_list: print(f"Prime numbers between {start_num} and {end_num}:") print(prime_list) else: print(f"No prime numbers found between {start_num} and {end_num}.")
Output:
Enter the starting number: 10
Enter the ending number: 100
Prime numbers between 10 and 100:
[11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]