isprime function

[nevets04]

I made this function to check whether a number was prime or not.
This was developed using codepad.org to test it during my 15 minute study hall. So it's simple, but it does work as far as I can see.

Code:

#!/usr/bin/env python
def isprime(n):
    if n > 10:
        if n%2 == 0 or n%3 == 0 or n%4 == 0 or n%5 == 0 or n%6 == 0 or n%7 == 0 or n%8 == 0 or n%9 == 0 or n%10 == 0:
            return False
        else:
            return True
    if n <= 10:
        if n == 2 or n == 3 or n == 5 or n == 7:
            return True
        if n == 1 or n == 4 or n == 6 or n ==8 or n == 9 or n == 10:
            return False

[uber1337]

Seems to be effective, you could have shortened it a bit though

Code:

#!/usr/bin/env python
def isprime(n):
    if n > 10:
        for x in range(2, 11):
            if n%x == 0: return False
        else:
            return True
    if n <= 10:
        if n in (2, 3, 5, 7): return True
        if n in (1, 4, 6, 8, 9, 10): return False

I can see your a little rusty

[Fallen]

Code:

if n in (2, 3, 5, 7): return True
        if n in (1, 4, 6, 8, 9, 10): return False

I can see your a little rusty

Code:

return False if n in [1, 4, 6, 8, 9, 10] else True

You are aswell

[uber1337]

Code:

return False if n in [1, 4, 6, 8, 9, 10] else True

You are aswell

LOL you really need to stop shortening things lol. Why don't you just use C++ and have a full length program on one line?

[symetrik]

Code:

#!/usr/bin/env python
def isprime(n):
    if n > 10:
        for x in range(2, 11): if n%x == 0: return False
        else: return True
    if n <= 10: return False if n in [1, 4, 6, 8, 9, 10] else True

Defeated by:

Code:

if isprime(x) and x > 11: isprime(x**x)

For example:

Code:

if isprime(13) and x > 11: # Will return true, as 13 is a prime and is larger than 10.
    isprime(13**13) # As 13 is not in the check list, this number will be found to be a prime, even though it clearly is not.

[wat]

Your function assumes that all composite numbers above 10 are divisible by a number smaller than 10; not true.

Here's an article explaining some of the intricacies that go into finding prime numbers .

Keep in mind that the first method mentioned could be optimized more by only checking numbers smaller than sqrt(num) instead of num / 2.