The answer is "yes, but…"

The best way to understand is to actually try it:

>>> class RLCN:
...     static_var = 5
...     def method1(self):
...         RLCN.static_var += 1
...     def method2(self):
...         self.static_var += 1
>>> rlcn = RLCN()
>>> RLCN.static_var, rlcn.static_var
(5, 5)
>>> rlcn.static_var
5
>>> rlcn.method1()
>>> RLCN.static_var, rlcn.static_var
(6, 6)
>>> rlcn.method2()
>>> RLCN.static_var, rlcn.static_var
(6, 7)

What happened?

Well, accessing a class attribute through self works just fine. If there is no instance attribute of the same name, you get the class attribute.

But assigning to it will hide the class attribute with a new instance attribute of the same name. Which is probably not what you wanted.

Note that this means you can use class attributes as "default values" or "initial values" for instance attributes. But I'm not sure it's very Pythonic to do so; what's actually happening, and what a novice (especially someone coming from, e.g., C++11 or Java) thinks is happening, are very different.

(Things get slightly more complicated when you deal with descriptors, like methods or @propertys, but let's ignore that; in the simple case that you're discussing, it's not relevant.)

I'd rather do something like class(self).static_var += 1, because long names are unreadable.

You can, you just need to spell it right: type is the function that returns the type of any object. So:

type(self).static_var += 1

This has the added advantage of being dynamic (e.g., when you have multiple inheritance and don't know which side a @property comes from, you probably don't want to explicitly list a class name, for basically the same reason you want to use super() instead of explicitly calling a base class method).

This has the disadvantage of not working on old-style classes in Python 2.x, but then you shouldn't be using those anyway. Especially in classes that have a need for class attributes, because those are exactly the types you're often going to later want to add @classmethods, @propertys, etc. to, and none of that works with old-style classes (along with many other things). If you really need to handle old-style and new-style classes transparently for some reason, self.__class__ is works with old-style classes. I'm not sure it's guaranteed to work with new-style classes; the docs say that the return value of type(object) is "generally the same object as returned by object.__class__", but doesn't say under what conditions that "generally" is untrue. It's also documented as a special attribute "added by the implementation" for "several object types" in 3.x. In practice, I don't know of any cases where they're different in 3.x, and in 2.x, the most prominent case where they're different is old-style classes.

Is this what you want to achieve?

class a:
    var = 0

    def foo(self):
        print(self.var)

b = a()

b.foo()  # "print(b.var)" also works

Above code gives the following result:

0

The answer, in a few words

In your example, itsProblem is a local variable.

Your must use self to set and get instance variables. You can set it in the __init__ method. Then your code would be:

class Example(object):
    def __init__(self):
        self.itsProblem = "problem"


theExample = Example()
print(theExample.itsProblem)

But if you want a true class variable, then use the class name directly:

class Example(object):
    itsProblem = "problem"


theExample = Example()
print(theExample.itsProblem)
print (Example.itsProblem)

But be careful with this one, as theExample.itsProblem is automatically set to be equal to Example.itsProblem, but is not the same variable at all and can be changed independently.

Some explanations

In Python, variables can be created dynamically. Therefore, you can do the following:

class Example(object):
    pass

Example.itsProblem = "problem"

e = Example()
e.itsSecondProblem = "problem"

print Example.itsProblem == e.itsSecondProblem 

prints

True

Therefore, that's exactly what you do with the previous examples.

Indeed, in Python we use self as this, but it's a bit more than that. self is the the first argument to any object method because the first argument is always the object reference. This is automatic, whether you call it self or not.

Which means you can do:

class Example(object):
    def __init__(self):
        self.itsProblem = "problem"


theExample = Example()
print(theExample.itsProblem)

or:

class Example(object):
    def __init__(my_super_self):
        my_super_self.itsProblem = "problem"


theExample = Example()
print(theExample.itsProblem)

It's exactly the same. The first argument of ANY object method is the current object, we only call it self as a convention. And you add just a variable to this object, the same way you would do it from outside.

Now, about the class variables.

When you do:

class Example(object):
    itsProblem = "problem"


theExample = Example()
print(theExample.itsProblem)

You'll notice we first set a class variable, then we access an object (instance) variable. We never set this object variable but it works, how is that possible?

Well, Python tries to get first the object variable, but if it can't find it, will give you the class variable. Warning: the class variable is shared among instances, and the object variable is not.

As a conclusion, never use class variables to set default values to object variables. Use __init__ for that.

Eventually, you will learn that Python classes are instances and therefore objects themselves, which gives new insight to understanding the above. Come back and read this again later, once you realize that.

There are two ways to access it

first: self.__class__.PAD_token

second: self.PAD_token

If you just need to access class variables, the first one is recommended