Manager.py

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#!/usr/bin/env python
'''
Usage
'''

class ObjectSet(object):
    '''Base (abstract) Manager for a colection of certain classes of objects'''
    
    def __init(self):
        '''
        Do not call this function in the child class.
        This is a boilerPlate for Child class's __init__(). 
        Intentionally wrong name to avoid reloading __setattr__().
        Child class mush define in its __init__() the following:
            - self.classForManaging : a tuple of classes of the managed objects
            - self.description : an empty dict for bookkeeping the attributes
        '''
        self.classForManaging = (None,)     
        # description = {name: class} for bookkeeping the attribute
        self.description = {}  

    # ---------------------------------------  
    def all_dict(self):
        '''return the dictionary of name:object of the managed classes'''
        return dict((name, self.__dict__[name]) for name in self.description)
        
    # ---------------------------------------  
    def all(self):
        '''return a list of objects of the managed classes'''
        return (self.__dict__[name] for name in self.description)
            
    # ---------------------------------------
    def __setattr__(self, name, value):      
        '''hook for caching a name of the Object as the class attribute'''
        object.__setattr__(self, name, value)        
        if isinstance(value, self.classForManaging):
            # The attribute class is intentionally only intialized once.
            # This way, one can intialize an attribute with a specific class
            # but can later use intrisic python type to represent this class
            # see the implemetation of class ParameterSet for an example
            self.description.setdefault(name, value.__class__)

    # # ---------------------------------------
    # def __getattr__(self, name):      
    #     '''hook for getting the Object given the attribute''' 

    # ---------------------------------------
    def add(self, name, anObject):
        """Add one Object"""
        if isinstance(anObject, self.classForManaging):
            self.__setattr__(name, anObject)
            return anObject
        raise AttributeError(str(anObject) 
            + ' is not a ' 
            + str(self.classForManaging))
        
    # ---------------------------------------
    def get(self, name):
        """Get the Object given the name"""
        try:
            objName = self.description[name]
        except KeyError:
            raise AttributeError('Object ' + name + ' is not defined yet')
        return self.__dict__[name]