On Jul 15, 12:36 pm, defn noob <[EMAIL PROTECTED]> wrote: > On Jul 15, 7:28 pm, Mensanator <[EMAIL PROTECTED]> wrote: > > > > > > > On Jul 15, 11:26 am, defn noob <[EMAIL PROTECTED]> 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. > > def isPrime(nbr): > for x in range(2, nbr + 1): > if nbr % x == 0: > break > if x == nbr: > return True > else: > return False > > this works for all primes, if i want to not include 1 i just do if > nbr<=1 return false > > you are answering the wrong question.
No, I also mentioned the for loop having an invalid range, which is why your original failed. Pointing out that 1 isn't prime was a bonus. > > anyway here is a clear one: > def isPrime(nbr): > if nbr < 2: > return False > for x in range(2, nbr + 1): > if nbr % x == 0: > return nbr == x I suppose you're not interested in knowing you don't have to test anything higher than the square root of the number. -- http://mail.python.org/mailman/listinfo/python-list
