Multiple object instance sharing global variable in Python

Question

I want to have a global variable x that can be accessed by multiple object instances: The module Obj should have something like:

x = 0

class Obj:  
  def set_x(self):    
      global x
      x = 2

  def print_x(self):    
      print x

...etc.

The other module (ex: main) instantiates the object obj:

obj1 = Obj.Obj()
obj1.set_x()
obj2 = Obj.Obj()
obj2.print_x

this should print 2

OK... so what is your question? Also, why wouldn't you just use a class attribute for that? — kindall, Nov 28 '11 at 07:31
Instance methods take ``self`` as the first argument. I have edited the code in the question. — codeape, Nov 28 '11 at 07:41
Whats ur question? When you tried wht did you get as output? — M S, Nov 28 '11 at 07:55
I just copied and pasted your code into an Idle session, and it works as-is. — Ben, Nov 28 '11 at 08:10

score 2 · Answer 1 · edited May 23 '17 at 12:27

2

I think you're looking for something like static variables (I'm not sure what they're called in Python). Have you tried something like:

class Obj:
   x = 0

   def set_x(self):
      Obj.x = Obj.x + 1

   def print_x(self):
      print Obj.x

Tests:

>>> obj1 = Obj()
>>> obj1.set_x()
>>> obj1.print_x()
1
>>> obj2 = Obj()
>>> obj2.set_x()
>>> obj2.print_x()
2
>>> obj1.print_x()
2

You should see this SO post for some more information.

edited May 23 '17 at 12:27

Community

answered Nov 28 '11 at 07:54

Dirk

What C calls "static variables" are called "global variables" in Python (even though they're not truly global). That is what the code sample in the question uses. The type of variable you're using here is called a "class attribute." – David Z Nov 28 '11 at 09:46
@dirk, thanks about user queryset issue comment in my answer (in other question). +1 – dani herrera Jan 29 '12 at 21:32

1 Answers1