Python Prime numbers

Let´s how to do a simple python program where we will check if a number is prime or not

First we define the variable that will have the number that we want to know if it´s a primer number or not

num = 29

Then we definde the variable that will have on it a Boolean(true or false value)

flag = False

Since prime numbers are greater than 1 we will start telling the program that checks if the num variable is greater than 1

if num > 1:

Inside the if statement we put a loop that will check in range from 2 until the value of the num variable that right now is 29

if num > 1:
  for i in range(2, num):

Now inside the for loop we will check if the module of num % i is 0 and if it´s it will mean that the number is not prime because it will have more dividers others than 1 and it´s self.

What is break?
break is a word in python that makes a break on the code or to be precise on the loop.

if num > 1:
  for i in range(2, num):
  if (num % i) == 0:
            flag = True
            break

The last part will check if the variable flag is true or false and depending what is it will display if the num variable is a prime number or not.

if flag:
    print(num, "is not a prime number")
else:
    print(num, "is a prime number")

Here is how will look the entire code

num = 29

flag = False

if num > 1:
    # check for factors
    for i in range(2, num):
        if (num % i) == 0:
            # if factor is found, set flag to True
            flag = True
            # break out of loop
            break

if flag:
    print(num, "is not a prime number")
else:
    print(num, "is a prime number")

That´s it for now.

Tip:
If you want the num variable to be an user input you can do this instead when defining the variable

num = int(input("Enter a number: "))

Shorter way to do it

num = 11

if num > 1:
    for i in range(2, num):
        if (num % i) == 0:
            print(num, "is not a prime number")
            break 
        elif(num % i) != 0:
            print(num, "num is a prime")
            break