Certainly! Here's a Python code snippet to check if a number is prime or not, with a focus on efficiency, readability, and edge-case handling: ```python def is_prime(n): """ Check if a number is prime. Parameters: n (int): The number to check. Returns: bool: True if the number is prime, False otherwise. """ # Edge case handling if not isinstance(n, int): raise ValueError("Input must be an integer.") if n <= 1: return False if n <= 3: return True if n % 2 == 0 or n % 3 == 0: return False # Check for factors from 5 to sqrt(n) i = 5 while i * i <= n: if n % i == 0 or n % (i + 2) == 0: return False i += 6 return True # Example usage: if __name__ == "__main__": test_numbers = [2, 3, 4, 5, 16, 17, 18, 19, -5, 1.5] for num in test_numbers: try: result = is_prime(num) print(f"{num} is prime: {result}") except ValueError as e: print(f"Error checking {num}: {e}") ``` ### Explanation: 1. **Edge Case Handling**: - **Non-integer Input**: Checks if the input is an integer. If not, raises a `ValueError`. - **Negative Numbers and Zero**: Numbers less than or equal to 1 are not prime by definition. 2. **Initial Checks**: - **Immediate Return for Small Values**: Handles numbers 2 and 3 directly (both are prime). It also eliminates even numbers and multiples of 3 quickly. 3. **Efficient Prime Checking**: - **Only Check Up to sqrt(n)**: We only need to check up to the square root of `n` for factors. This reduces the number of checks significantly. - **6k ± 1 Optimization**: After checking for divisibility by 2 and 3, we can use a step of 6 to check potential factors. This skips over numbers that are obviously not prime (i.e., multiples of 2 and 3). ### Example Usage: To test the code, simply run the script. It will print whether each number in `test_numbers` is prime or not, and handle errors for non-integer inputs gracefully. Adjust `test_numbers` as needed to test different values.