classes and interfaces

[Bruno Desthuilliers]

s99999999s2003 at yahoo.com wrote:
> hi
> i come from a non OO environment. now i am learning about classes. can
> i ask, in JAva, there are things like interface. eg
> public interface someinterface {
>    public somemethod ();
>    ....
>    ...
> }
> 
> In python , how to implement interface like the above? is it just
> define a class??

Java interfaces are a workaround the combination of static typing
(limiting polymorphism) and lack of multiple inheritance. Since Python
is dynamically typed (polymorphism does not depend on type), there's no
such need:

class Foo(object):
  def doThis(self):
    print "in Foo.doThis"

class Bar(object):
  def doThis(self):
    print "in Bar.doThis"

def doIt(obj):
  obj.doThis()

f = Foo()
b = Bar()

doIt(f)
doIt(b)

A you can see, doIt() works for any object having a doThis() method. No
need for inheritance or interface here.

Note that we do have something like interfaces (in some third-part
librairies), but with a somewhat different (and much more powerful) usage:

http://peak.telecommunity.com/protocol_ref/ref.html

But if you're new to OO, this may not be the best starting point !-)

-- 
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'onurb at xiludom.gro'.split('@')])"