Static variable inheritance in Python

Question

I'm writing Python scripts for Blender for a project, but I'm pretty new to the language. Something I am confused about is the usage of static variables. Here is the piece of code I am currently working on:

class panelToggle(bpy.types.Operator):
    active = False

    def invoke(self, context, event):
        self.active = not self.active
        return{'FINISHED'}

class OBJECT_OT_openConstraintPanel(panelToggle):
    bl_label = "openConstraintPanel"
    bl_idname = "openConstraintPanel"

The idea is that the second class should inherit the active variable and the invoke method from the first, so that calling OBJECT_OT_openConstraintPanel.invoke() changes OBJECT_OT_openConstraintPanel.active. Using self as I did above won't work however, and neither does using panelToggle instead. Any idea of how I go about this?

Solution 1

use type(self) for access to class attributes

>>> class A(object):
 var  = 2
 def write(self):
  print type(self).var
>>> class B(A):
 pass
>>> B().write()
2
>>> B.var = 3
>>> B().write()
3
>>> A().write()
2

Solution 2

You can access active through the class it belongs to:

if panelToggle.active:
    # do something

If you want to access the class variable from a method, you could write:

def am_i_active(self):
    """ This method will access the right *class* variable by
        looking at its own class type first.
    """
    if self.__class__.active:
        print 'Yes, sir!'
    else:
        print 'Nope.'

A working example can be found here: http://gist.github.com/522619

---

The self variable (named self by convention) is the current instance of the class, implicitly passed but explicitely recieved.

class A(object):

    answer = 42

    def add(self, a, b):
        """ ``self`` is received explicitely. """
        return A.answer + a + b

a = A()

print a.add(1, 2) # ``The instance -- ``a`` -- is passed implicitely.``
# => 45

print a.answer 
# => print 42