Judge whether it is a prime number [Python]

In this article A program that determines whether the input value (n) is a prime number or not. I will write.

What is a prime number?

A prime number is a natural number greater than 1 that has only one positive divisor and itself. See: prime numbers-Wikipedia

Execution environment

• MacOS
• Python 3.7.5

How to find

(1) If it is 1 or less or 2, describe whether it is a prime number. (2) If it is 3 or more, loop from 2 to n and check if there is a divisible number. If it is divisible, it is not a prime number. ③ Call the function and display the result.

** There was an error in the case of an integer greater than or equal to 3, so I corrected it **

(1) If it is 1 or less or 2, describe whether it is a prime number.

If False, it is not a prime number. If True, a prime number.

prime_num.py

def is_prime(n):
    #1 or less is not a prime number
    if n <= 1:
        return False
    #2 is a prime number
    if n == 2:
        return True

(2) If it is 3 or more, loop from 2 to n and check if there is a divisible number.

If it is divisible, it is not a prime number

prime_num.py(2)

def is_prime(n):
    #1 or less is not a prime number
    if n <= 1:
        return False
    #2 is a prime number
    if n == 2:
        return True
    #Even numbers other than 2 are not prime numbers
    if n % 2 == 0:
        return False
    #For odd numbers of 3 or more, prime numbers unless divisible by all odd numbers up to the square root
    return all(n % i != 0 for i in range(3, int(n**0.5) + 1, 2))

③ Call the function and display the result

If False, it is not a prime number. If True, it is a prime number.

prime_num.py(3)

def is_prime(n):
    #1 or less is not a prime number
    if n <= 1:
        return False
    #2 is a prime number
    if n == 2:
        return True
    #Even numbers other than 2 are not prime numbers
    if n % 2 == 0:
        return False
    #For odd numbers of 3 or more, prime numbers unless divisible by all odd numbers up to the square root
    return all(n % i != 0 for i in range(3, int(n**0.5) + 1, 2))

number = int(input("Natural number →"))

if is_prime(number):
    print(f"{number}Is a prime number.")
else:
    print(f"{number}Is not a prime number.")

Execution result

number = 1
→ 1 is not a prime number.

number = 5
→ 5 is a prime number.

The result is reflected.

Summary

This time, I wrote a program to judge whether it is a prime number in Python.

In this program, the larger n is, the longer the calculation becomes. I would like to find more efficient code.

reference

prime number --Wikipedia