How to learn OO of python?

[could ildg]

Thanks very much to Harlin Seritt.
Your example is really helpful to me.

I read some more docs on python oop and I am more clear
now. But when I try to understand Decorators for Functions and Methods
in PEP 318, I got puzzled. How do Decorators work? 

I think decorator is a function which return a function, is this right?
e.g. The decorator below if from http://www.python.org/peps/pep-0318.html#id1.

def accepts(*types):
    def check_accepts(f):
        assert len(types) == f.func_code.co_argcount
        def new_f(*args, **kwds):
            for (a, t) in zip(args, types):
                assert isinstance(a, t), \
                       "arg %r does not match %s" % (a,t)
            return f(*args, **kwds)
        new_f.func_name = f.func_name
        return new_f
    return check_accepts

After I saw all the examples, I concluded that every decorator must
define an inner function which takes only one argument, the
function to decorate. Is this right?

On 5/18/05, Harlin Seritt <harlinseritt at yahoo.com> wrote:
> could ildg wrote:
> > I have learned python for over a month.
> > I heard that it was very easy to learn, but when I tried to know OO
> of python,
> > I found it really weird, some expressions seem very hard to
> understand,
> > and I can't find enough doc to know any more about it.
> > So, I wonder how did you master python? And where to find some cool
> docs?
> >
> > Thanks.
> 
> I think I know what you mean. When I first started trying to learn the
> OOP aspect of Python I thought it was strange since I had started with
> OOP on Java and C++. Nonetheless, once you get the hang of it, OOP will
> make way more sense than all of the complications of Java and C++ class
> implementations. Let me give you a quick example of what I'm talking
> about:
> 
> class Animal:
>    def eats(self):
>       print 'The animal eats.'
>    def walks(self):
>       print 'The animal walks.'
> 
> """Here the class Dog instantiates the class Animal. 'Dog' will 'do'
> whatever 'Animal' does plus some other things which we will describe in
> this class code."""
> class Dog(Animal):
>    """#the self keyword means that this function will be a class
> function"""
>    def communicate(self):
>       print 'The dog barks.'
> 
>    """# __init__ function defines what # #will happen as soon as this
> class is instantiated. Also, the overloaded variable designators (color
> = None, fur = None) allow the instantiator to optionally define these
> variables when called from elsewhere."""
> 
>    def __init__(self, color=None, fur=None):
>       """# this time self will designate the variable 'color' # as a
> class variable."""
>       self.color = color
>       self.fur = fur
> 
> if __name__ == '__main__':
>    sparky = Dog(color="White", fur="Short")
>    sparky.communicate()
>    print sparky.color
>    print sparky.fur
>    print sparky.eats()   # Here sparky will access 'Animal' methods
> that 'Dog' inherited.
>    print sparky.walks()  # Another method originating from the 'Animal'
> class.
> 
> What happens if you don't use 'self' inside your class code? You won't
> be able to access it within the class outside of the method where you
> initialized it. For instance, if you don't designate color with self
> then you can only use the 'color' variable within the __init__()
> method. This is useful whenever you want to use 'color' as a private
> variable.
> 
> The same also goes for methods. Hopefully, you see how useful this can
> be down the road. This way you won't have to use variable/method access
> modifiers like Public, Private, Protected and so forth. If this doesn't
> make sense or you want more clarity, please let me know.
> 
> Good luck,
> 
> Harlin Seritt
> 
>