[Tutor] intefaces in python

[Andre Engels]

On Sun, Jun 28, 2009 at 5:00 PM, Amit Sethi<amit.pureenergy at gmail.com> wrote:
> Hi , I don't suppose python has a concept of interfaces. But can somebody
> tell me if their is a way i can  implement something like a java interface
> in python.

Sure. Interfaces are just Java's compensation for not having multiple
inheritance. Python does have multiple inheritance, so that's what one
would use. Although one could also use duck typing, and then use
'nothing' as an implementation...

More specific:

========================
Java Interface:
public interface MyInterface {
    string doSomething(string line);
    string doSomethingElse(string line);
}

Java Implementation:
public class MyImplementation {
   string doSomething(string line) {
       return "I did something with" + line;
   }
   string doSomethingElse(string line) {
      return "I did something else."
   }
}

==============================
Python Interface:

class MyInterface(object):
    doSomething(line):
        raise NotImplementedError
    doSomethingElse(line):
        raise NotImplementedError

Python Implementation:
class MyImplementation(MyInterface):
    doSomething(line):
        return "I did something with "+line
    doSomethingElse(line):
        return "I did something else."

==============================
Python interface using duck typing:

# Hey guys, when you call something a 'MyInterface', it needs methods
doSomething and doSomethingElse

Python Implementation using duck typing:

class MyImplementation(object):
    # These things implement MyInterface
    doSomething(line):
        return "I did something with "+line
    doSomethingElse(line):
        return "I did something else."


-- 
André Engels, andreengels at gmail.com