Should I be using “global” or “self.” for class scope variables in Python?

Question

Both of these blocks of code work. Is there a \"right\" way to do this?

class Stuff:
    def __init__(self, x = 0):
        global globx
        globx = x
          


        

Answer 1

There are 2 ways for "class scope variables". One is to use self, this is called instance variable, each instance of a class has its own copy of instance variables; another one is to define variables in the class definition, this could be achieved by:

class Stuff:
  globx = 0
  def __init__(self, x = 0):
    Stuff.globx = x 
  ...

This is called class attribute, which could be accessed directly by Stuff.globx, and owned by the class, not the instances of the class, just like the static variables in Java.

you should never use global statement for a "class scope variable", because it is not. A variable declared as global is in the global scope, e.g. the namespace of the module in which the class is defined.

namespace and related concept is introduced in the Python tutorial here.