Having problems defining variables outside a function (Python)

Question

I'm pretty new to python and I'm trying to make a simple program where you have text menus and I have to use functions to do most of the work (to get used to using functions inside a program). So I'm trying to use a function in this program to get the first, second, and possibly a third number from the user. I need to be able to reuse this function so I can get said numbers from the user, but I'm having problems with only being able to use these variables within the function and nowhere else. Any suggestions will help! Here's the code:

option = 1
while option !=0:
    print "\n\n\n************MENU************"
    print "1. Counting by one"
    print "2. Fibbonacci Sequence"
    print "0. GET ME OUTTA HERE!"
    print "*" * 28

    option = input("Please make a selection: ") #counting submenu
    if option == 1:
        print "\n\n**Counting Submenu**"
        print "1. Count up by one"
        print "2. Count down by one"
        print "3. Count up by different number"
        print "4. Count down by different number"

        countingSubmenu = input("Please make a selection: ")
        def getNum():
            firstNum = input("Please state what number to start at: ")
            secondNum = input("Please state what number to end at: ")
            if countingSubmenu == 3 or countingSubmenu == 4:
                thirdNum = input("Please state what increment you would want to go up by: ")

         if option == 1:
             getNum()
             for x in range(firstNum, secondNum+1):
                print x
             print "End of test."

Any variables that you declare within a function don't exist outside of it. They are called local variables. If you want variables to exist outside of the function, you need to declare them outside of the function. — Hunter McMillen
– Hunter McMillen, Commented Aug 15, 2011 at 17:35

Ned Batchelder · Accepted Answer · 2011-08-15 17:50:16Z

5

Variables are local to the functions in which they are defined. You might try having your function return those values:

def getNum():
    firstNum = input("...")
    secondNum = input("...")
    thirdNum = input("...")
    return firstNum, secondNum, thirdNum

if option == 1:
    firstNum, secondNum, thirdNum = getNum()

answered Aug 15, 2011 at 17:50

Ned Batchelder

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3 Comments

spacediver Over a year ago

Yeah, returning a tuple is quite straightforward and pythonic way of performing this task.

user895344 Over a year ago

Could you explain the Pythonic logic behind having the variables equal a function?

user895344 Over a year ago

Yea, I'm getting a 'NoneType' object is not iterable when I try to implement that into my code. :/

Sinthet · Accepted Answer · 2011-08-15 17:58:17Z

1

Alternatively, you could use global variables. For example:

global a_var
  def a_function():
   global a_var   
   a_var = 3

a_function()
print a_var

However, using a return is probably cleaner.

answered Aug 15, 2011 at 17:58

Sinthet

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