> Hello,
>
> I tried it with this simple programm
>
> def is_prime(n):
> x=2
> while x <= int(n**0.5)+1:
> if n % x == 0:
> return False
If your while condition is True, you get into the loop.
Inside the loop, however, you never change anything that could change the
condition (ie, neither x nor n get changed).
So the while condition stays the same, ie, True, and you loop indefinitely.
> x=x+1;
Ah, but here you actually change something so that the while condition could
become False. Sadly, this statement is outside the loop (hint hint).
>
> return True
>
> x=is_prime(7)
> if x==True:
> print 7, "is een prime getal"
> else :
> print 7, "is geen prime getal"
>
>
> But this one gets in a indefinitive loop.
Try to mentally follow the logic of the loop.
Or use print statements and some small, easily checkable, numbers (prime and
non-prime) to see what happens.
Print statements (functions, if you're on Python >= 3) are a simple, but at
times extremely quick and useful way to debug scripts.
Ah yes, and either use "is een priemgetal" or "is a prime number", not a mix of
both (sorry, couldn't help myself ;-).
Evert
>
> Roelof
>
>
> > From: st...@pearwood.info
> > To: tutor@python.org
> > Date: Sun, 22 Aug 2010 02:49:26 +1000
> > Subject: Re: [Tutor] prime test problem
> >
> > On Sun, 22 Aug 2010 12:41:03 am Roelof Wobben wrote:
> > > Hello,
> > >
> > > I know.
> > > I have read them all I believe
> >
> > You've read all 64 million pages that Google finds? Wow, you must be a
> > fast reader! Well done!
> >
> > > but I can't see how I can convert the
> > > algebra to a working programm.
> >
> > Have you *tried*?
> >
> > Perhaps you should try something a little bit less ambitious. Write a
> > program to test whether a number is divisible by 3. Then write a
> > program to test whether a number is divisible by 3 or 5. Then write a
> > third program to test whether a number is divisible by 3, 5 or 7.
> >
> > Then generalise that third program.
> >
> > Off you go. Come back when you have some code. Even if it isn't working
> > code, at least try something.
> >
> >
> >
> > --
> > Steven D'Aprano
> > _______________________________________________
> > Tutor maillist - Tutor@python.org
> > To unsubscribe or change subscription options:
> > http://mail.python.org/mailman/listinfo/tutor
> _______________________________________________
> Tutor maillist - Tutor@python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
