Class NameError: name 'var' is not defined

Question

class Gui():
    var = None
    def refreshStats(args):
        print(str(var))
clas = Gui()
clas.refreshStats()

Trace

File "sample.py", line 5, in refreshStats
    print(str(var))
NameError: name 'var' is not defined.

Why?

You have made `var` a class attribute belonging to the `Gui` class, so you'd have to access it as `Gui.var`. — khelwood, Apr 18 '17 at 17:36
You're missing a `self` parameter on `refreshStats`, by the way (unless you intend `args` to be the class) — OneCricketeer, Apr 18 '17 at 17:37
@cricket_007: nope, that would cause an error. technically the OP just renamed it... — Karoly Horvath, Apr 18 '17 at 17:38

ClydeTheGhost · Accepted Answer · 2017-04-18T17:47:26.197

1

If you want your variables to be visible within the scope of your class functions, pass self into every class function and use your class variables as self.var such as this:

class Gui():
    var = None
    def refreshStats(self, args):
        print(str(self.var))
clas = Gui()
clas.refreshStats()

If you want to use this as an instance variable (only for this instance of the class) as opposed to a class variable (shared across all instances of the class) you should be declaring it in the __init__ function:

class Gui():
    def __init__(self):
        self.var = None
    def refreshStats(self, args):
        print(str(self.var))
clas = Gui()
clas.refreshStats()

edited Apr 18 '17 at 17:47

answered Apr 18 '17 at 17:39

ClydeTheGhost

1,473
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31

And what if the class variable was intentional? – OneCricketeer Apr 18 '17 at 17:41
You also should be initializing your class variables in an init function. see edits – ClydeTheGhost Apr 18 '17 at 17:41
That's called an instance variable, not a class variable – OneCricketeer Apr 18 '17 at 17:42
Quite right, I hope my edits have clarified things – ClydeTheGhost Apr 18 '17 at 17:47

score 1 · Answer 2 · answered Apr 18 '17 at 17:44

make method inside class either classmethod or instance method then you can access all class instance property or varable inside method if method is instance method or if class method then class property you can access inside method

class A():
     a = 0

     def aa(self):
         """instance method"""
         print self.a

     @classmethod
     def bb(cls):
         """class method"""
         print cls.a

score 0 · Answer 3 · 2017-04-18T17:47:26.677

0

var is not defined in the scope of your refreshStats() function, as it is a class variable.

As such, if you want to access it, you can do Gui.var.

edited Apr 18 '17 at 17:47

answered Apr 18 '17 at 17:37

1

This is basically just rewording the error message without explaining *why* `var` is not defined. – chepner Apr 18 '17 at 17:38
@chepner hopefully more useful now – Apr 18 '17 at 17:48

Class NameError: name 'var' is not defined

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