Static attributes (Python vs Java)

Question

What is the difference between Python class attributes and Java static attributes?

For example,

in Python

class Example:
    attribute = 3

in Java

public class Example {

    private static int attribute;

}

In Python, a static attribute can be accessed using a reference to an instance?

Answer 1

In Python, you can have a class variable and an instance variable of the same name [Static class variables in Python]:

>>> class MyClass:
...     i = 3
...
>>> MyClass.i
3 

>>> m = MyClass()
>>> m.i = 4
>>> MyClass.i, m.i
>>> (3, 4)

In Java, you cannot have a static and non-static field with the same name (the following will not compile, you get the error "Duplicate field MyClass.i"):

public class MyClass {
  private static int i;
  private int i;
}

additionally, if you try to assign a static field from an instance, it will change the static field:

public class MyClass {
  private static int i = 3;

  public static void main(String[] args) {
    MyClass m = new MyClass();
    m.i = 4;

    System.out.println(MyClass.i + ", " + m.i);
  }
}

4, 4

---

In both Java and Python you can access a static variable from an instance, but you don't need to:

Python:

>>> m = MyClass()
>>> m.i
3
>>> MyClass.i
3

Java:

  public static void main(String[] args) {
    System.out.println(new MyClass().i);
    System.out.println(MyClass.i);
  }

3
3