composition and aggregation in python

Question

I want to know how to implement composition and aggregation in UML terms in python.

If I understood:

1. Aggregation:

Answer 1

# Aggregation is NOT exclusive
class BaseChapter:
    '''
    We can use this BaseChapter in any book, like in OpenBook.
    '''

    def __init__(self, name):
        self.name = name
        self.subject = None
        self.content = None
        return

class OpenBook:

    def __init__(self, isbn):
        self.isbn = isbn
        self.chapters = list()

    def add_chapter(self, obj):

        # This constrain dont have correlation with composition/aggregation
        if isinstance(obj, BaseChapter):
            self.chapters.append(obj)
        else:
            raise TypeError('ChapterError')

# .. but Composition is Exclusive
# Example:
class MyBook:

    class MyChapter:
        '''
        This MyChapter can be used only by MyBook
        '''
        def __init__(self, name, subject):
            self.name = name
            self.subject = subject
            self.title = None
            self.content = None
            self.techincal_refs = list()
            return

    def __init__(self, isbn):
        self.isbn = isbn
        self.chapters = list()

    def add_chapter(self, obj):
        # This constrain dont have correlation with composition/aggregation
        # what is important here is MyChapter can be used only by MyBook
        # a outside object cant create a instance of MyChapter
        if isinstance(obj, self.MyChapter):
            self.chapters.append(obj)
        else:
            raise TypeError('ChapterError')

.. and yes we can do better like

class MyBook:

    class MyChapter(BaseChapter):
        '''
        This MyChapter can be used only by MyBook,
        but now is based in BaseChapter.
        But you knhow, python dont create problems if you still want
        create a instance of MyChapter in other 'Books'.

        But when you see this code you will think, This class is exclusive
        to MyBook.
        '''
        def __init__(self, name):
            super().__init__(name)
            self.subject = None
            self.title = None
            self.content = None
            self.techincal_refs = list()
            return

    def __init__(self, nib):
        self.nib = nib
        self.chapters = list()

    def add_chapter(self, obj):
        # This constrain dont have correlation with composition/agregation
        # what is important here is MyChapter can be used only by MyBook
        if isinstance(obj, self.MyChapter):
            self.chapters.append(obj)
        else:
            raise TypeError('ChapterError')