Global variables/ Classes

Question

I need to pass a value created within a class method to a function, or procedure or def or whatever it is called, in the 'main program'

global myValue

class CalcFrame(object):
        def clearFunc(self):
                myValue = 12

def getUrl():
        print myValue

This was my idea, obviously it does not work:

I do that code, then I create an object

x = CalcFrame()

call the method which should set the global

x.clearFunc()

then call the function which should print it

getUrl()

get the error

NameError: global name 'myValue' is not defined

possible duplicate of [Using global variables in a function other than the one that created them](http://stackoverflow.com/questions/423379/using-global-variables-in-a-function-other-than-the-one-that-created-them) — Uyghur Lives Matter, Jun 23 '15 at 20:48

score 7 · Accepted Answer · edited Jun 23 '15 at 20:44

This is not how the global keyword is used.

It should be used this way instead

myValue = None

class CalcFrame(object):
    def clearFunc(self):
            global myValue
            myValue = 12

In a nutshell, global allows a function to modify a variable that exists in the global scope. See here for more info: https://docs.python.org/2/faq/programming.html#what-are-the-rules-for-local-and-global-variables-in-python

1 Answers1