New user needs help

[John]

Thank you very much. This solved the problem. I now see where the problem
was. This was driving me bonkers! I'm sure I will post here frequently so
thanks in advance for everyone's help.

"omission9" <omission9 at invalid.email.info> wrote in message
news:64CZb.19719$wD5.7887 at nwrddc03.gnilink.net...
> John wrote:
>
> > I am new to using Python. Everytime I run this program it prints "The
lowest
> > common factor is 0", no matter what numbers I use. Can anybody see
anything
> > wrong with my program? Thanks in advance.
> >
> >
> >
> > def getnum1(a):
> >     a = input("What is the first number?")
> >     if a == 0:
> >         getnum1(a)
> > def getnum2(b):
> >     b = input("What is the second number?")
> >     if b == 0:
> >         getnum2(b)
> > def euclid(num1, num2, num3, num4):
> >     if num1 < num2:
> >         num3, num4 = num1, num2
> >         num1, num2 = num4, num3
> >         euclid(num1, num2, num3, num4)
> >     elif num2 != 0:
> >         num3, num4 = num1, num2
> >         num1 = num4
> >         num2 = num3 % num4
> >         euclid(num1, num2, num3, num4)
> >     else:
> >         print "The lowest common factor is: ", num1
> > a = 0
> > getnum1(a)
> > b = 0
> > getnum2(b)
> > x, y = 2, 100
> > euclid(a, b, x, y)
>
> This is a nice simple example of what is called "scope" and how it can
> trick a beginner.
> Put as simply as possible,"a" and "b" are actually defined twice. Once
> "locally" in the getnum functions and another time "globally" . When you
> set a and b to the user input in the functions the other a and b have no
> idea about this assignment. Below is a slight revision which return the
> a and b set by the user back to where they are called. By putting a
> simple print statement in the script you can see where the values are
> set and that can help you.
> I hope that helps. There is probbaly a couple of other changes you could
> make as well but nothing too major, in my opinion.
>
>
> def getnum1(a):
>      a = input("What is the first number?")
>      if a == 0:
>          getnum1(a)
>      return a
> def getnum2(b):
>      b = input("What is the second number?")
>      if b == 0:
>          getnum2(b)
>      return b
> def euclid(num1, num2, num3, num4):
>      print num1, num2, num3, num4
>      if num1 < num2:
>          num3, num4 = num1, num2
>          num1, num2 = num4, num3
>          euclid(num1, num2, num3, num4)
>      elif num2 != 0:
>          num3, num4 = num1, num2
>          num1 = num4
>          num2 = num3 % num4
>          euclid(num1, num2, num3, num4)
>      else:
>          print "The lowest common factor is: ", num1
> a = 0
> b = 0
> a=getnum1(a)
> b=getnum2(b)
> x, y = 2, 100
> euclid(a, b, x, y)
>