(Sep-16-2020, 11:54 AM)ebolisa Wrote: Your code fails!!

You may learn some from here https://www.programiz.com/python-programming/examples/odd-even

Nevermind. Your prime/not prime odd/even q was confusing.

def prime_num(a):
    counter=1
    if a>1:
        for x in range(2,a):
            if(a%x)==0:
                print("The number is NOT PRIME")
                counter=0
                break
        if(counter==1):
             print("The number is PRIME")
    else:
        print("Invalid Number")
        
print (prime_num(0))
print (prime_num(5))
print (prime_num(10))
print (prime_num(15))
print (prime_num(20))

def prime_num(a):
    counter=1
    if a>1:
        for x in range(2,a):
            if(a%x)==0:
                return ("The number is NOT PRIME")
                counter=0
                break
        if(counter==1):
             return ("The number is PRIME")
    else:
        return ("Invalid Number")
         
print (prime_num(0))
print (prime_num(5))
print (prime_num(10))
print (prime_num(15))
print (prime_num(20))

(Sep-16-2020, 01:40 PM)perfringo Wrote: You could consider more general approach to this function.

If objective is to determine whether number is prime or not then the answer can be yes or no which translates into Python as True or False. Of course, depending on specifics False may not be good enough (if for some reason distinction must be made between not primes and not valid numbers) but this is validation problem which should/could be dealt separately.

As for solution there is no need to test even numbers after 2 (if number doesn't divide with 2 then it is odd and will not divide with 4, 6, 8...). But.... you should also keep in mind that there is one even number among primes: 2. Upper limit should be not number itself but square root of the number which primality is to be tested. These are low hanging fruits which significantly reduce calculations needed.