isPrime works but UnBoundLocalError when mapping on list

[Mensanator]

On Jul 15, 11:26 am, defn noob <circularf... at yahoo.se> wrote:
> isPrime works when just calling a nbr but not when iterating on a
> list, why? adding x=1 makes it work though but why do I have to add
> it?
> Is there a cleaner way to do it?
>
> def isPrime(nbr):
>     for x in range(2, nbr + 1):
>         if nbr % x == 0:
>             break
>     if x == nbr:
>         return True
>     else:
>         return False
>
> >>> [isPrime(y) for y in range(11)]
>
> Traceback (most recent call last):
>   File "<pyshell#45>", line 1, in <module>
>     [isPrime(y) for y in range(11)]
>   File "C:\Python25\Progs\blandat\myMath.py", line 9, in isPrime
>     if x == nbr:
> UnboundLocalError: local variable 'x' referenced before assignment
>
> >>> map(isPrime, range(100))
>
> Traceback (most recent call last):
>   File "<pyshell#38>", line 1, in <module>
>     map(isPrime, range(100))
>   File "C:\Python25\Progs\blandat\myMath.py", line 9, in isPrime
>     if x == nbr:
> UnboundLocalError: local variable 'x' referenced before assignment>>> isPrime(10)
> False
> >>> isPrime(11)
>
> True
>
> adding x=1 makes it work though:
>
> def isPrime(nbr):
>     x=1
>     for x in range(2, nbr + 1):
>         if nbr % x == 0:
>             break
>     if x == nbr:
>         return True
>     else:
>         return False
>
> >>> [isPrime(y) for y in range(11)]
>
> [False, True, True, True, False, True, False, True, False, False,
> False]

No, it doesn't. You are falsely reporting that 1 is prime.

And instead of making the fake variable x, shouldn't you
instead test that nbr+1 is greater than 2? Or call it with
range(3,11) instead of range(11)? x isn't initialized
because if nbr+1 is <=2, the for loop has an invalid range
and doesn't even execute.