Python Classroom Series – 07/Aug/2020

Relationships (contd..)

  • Describe Object Oriented stuff diagrammatically we use UML (Unified Modelling Language)
  • I have oranges and i can place oranges in a basket
    • Orange is an object
    • basket is an object
  • There is a relationship b/w basket and oranges
  • To represent in basic class diagram Preview
  • When we specify a relationship b/w oranges and basket it is many oranges in one basket (many to one) Preview
  • Now lets try cardinality between bus and a conductor Preview
  • Line between two classes is association & numbers at the end of the line represent cardinality
  • Sample class diagram looks like (note this is not completely correct version) Preview

Lets try to design objects and their relationships in a library.

  • This library has
    • Books
    • DVDs
    • Magazines
    • CDs
  • The user are librarian and readers. Librarian gives a unique number (lib_id)
  • Librarian needs to locate the library items
  • Readers will also be given catalog where they can search for existence of book or not
  • Lets think of different classes
    • Book
    • DVD
    • Magazine
    • CD
    • Shelf
    • Catalog
  • Now lets speak normal english to come up with design
    • Book is a LibraryItem
    • DVD is a LibraryItem
    • Magazine is a LibraryItem
    • CD is a LibraryItem
    • Shelf has LibraryItem’s
  • Now the diagrammatic representation will be something like Preview


  • Create a diagram as shown above for the following problem statement
  • A Bank has a savings account, fixed deposit account, recurring deposit account and loan accounts
  • Bank Manager/Accountant would like to search with an account number using Account Console
  • Customers should be able to see account balance, last transactions
  • Also represent Transactions in the diagram.

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