isPrime works but UnBoundLocalError when mapping on list

[norseman]

defn noob 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]
> --
> http://mail.python.org/mailman/listinfo/python-list
> 

========================================
Yep - "local variable 'x' referenced before assignment" is correct.
You state: for x in range... but x doesn't exist until initialized.
   To save a loop, initialize x=2 (the minimum value) and loop executes
   on pass one.
In a straight 'C' program
   (  for (x=1, x=(nbr+1), x++)  etc...  )
   the x is initialized and forceably incremented.
   seems Python does not auto initialize but does auto increment.


Steve
norseman at hughes.net