[Tutor] Now I have a variable-passing problem!

[Glen Wheeler]

  Hi,

  Since I couldn't see anything written by Andrew to show an implementation
method that uses recursion, I thought I'd chuck one in.  True, it's better
using a loop but... some people just like recursion :)

> Now I've made the following mess for myself:

  heh :)

> def get_number():
>     rawNum=raw_input("Enter a number between 0 and 10,000: ")
>
>     try:
>         num_int = string.atoi(rawNum)
>         if (0 >  num_int) or (num_int > 10000):
>             print 'Sorry, that number is not between 0 and 10000'
>             rawNum = get_number()  # lest the value is lost in the wicked
maze of recursion :)
>
>
>     except ValueError:
>         print "Try again. We need an integer between 0 and 10,000"
>         get_number()
>
>     return rawNum
>
> <...>
>
> Here's what I don't understand: get_number() is called (function A) and
> assigns a raw input value to rawNum. When rawNum fails the "string.atoi"
> test, the function calls itself again (function B), assinging a new value
to
> rawNum which does not get passed to the function A when the function B
> terminates. How do I (re)write the code so that function B  passes the
> correct value to function A?
>
  Your code looks all well and good, but has a pretty major problem.  When
you recursively call get_number you aren't storing the value - something
like 'result = get_number()' is needed.  When you do this, you also need to
declare result (again, simple as 'result = None') and modify the return
statement.  So, only really one change but the new incarnation would be...

def get_number():
    rawNum=raw_input("Enter a number between 0 and 10,000: ")

    try:
        result = None # don't want an unbound var error...
        num_int = int(rawNum)
        if (0 >  num_int) or (num_int > 10000):
            print 'Sorry, that number is not between 0 and 10000'
            result = get_number()  # lest the value is lost in the wicked
maze of recursion :)

    except ValueError:
        print "Try again. We need an integer between 0 and 10,000"
        result = get_number() # ditto

    if result:
        return result
    else:
        return rawNum

> Should I even bother or just re-write the body of the if-test to re-prompt
> without a recursive call?
>

  It's not too much trouble to correctly recursify it, esp if you've already
built the function.

  Anywho, have fun :)
  Glen