Accessing container's methods

[Terry Reedy]

On 12/7/2015 1:10 PM, Tony van der Hoff wrote:
> Hi,
>
> I have a class A, containing embedded embedded classes, which need to
> access methods from A.
> .
> A highly contrived example, where I'm setting up an outer class in a
> Has-a relationship, containing a number of Actors. The inner class needs
> to access a method of the outer class; here the method get_name.
>
> I don't really want to make Actor a sub-class (is-a; it isn't) of Monty;
> that would raise all sorts of other problems.
>
> Can anyone please advise me on how to achieve this magic?
>
> # define the outer class
> class Monty:
>    def __init__( self, names ):
>      self.actors = []
>
>      i = 0
>      for n in names:
>        self.actors.append( Actor( n, i ) )
>        i += 1    # here is a case for python supporting post-increment!

This is actually a case for using enumerate:
   for i, name in enumerate(names):

>
>    def count_actors( self ):
>      return len( self.actors )
>
>    def list_actors( self ):
>      h=[]
>      for n in self.actors:
>        h.append( n.get_name() )
>      return h

return list(self.actors)  # or perhaps even faster
return self.actors[:]

> # define the inner class
> class Actor:
>    def __init__ ( self, name, id ):
>      self.name = name
>      self.id = id

Tkinter, and I presume tk, works by creating circular references.
widgets get a reference to a master widget, and container get a 
reference to widgets that are placed (or packed or gridded) therein. 
Widgets have an explicit .destroy method (inherited from tcl/tk) to undo 
the circularity.  It works, but it is not completely without problems.

-- 
Terry Jan Reedy