Session 9 - The python datamodel

Today we will look at the python datamodel.

Python has a protocol orientated datamodel.

After this you will be able to implement code in own classes that allow you to use pythons built-in functions or top level syntax to interact with these object.

Example:

If you want to be able to use the build in function len() on your object you should implement the __len__ method in your class.

If you want to be able to use the == operator on your object you should implement the __eq__ method in your class.

If you want to be able to use the in key word on your object you should implement the __contains__ method in your class.

Learning goals

• Create your own classes, that behave like any other Python Object, and are able to interact with pythons build in functions or top level syntax.

Materials

• What Does It Take To Be An Expert At Python?

  • This is a talk about expert python programming and this is what we will cover the rest of this semester. (Todays topic is from the beginning to 18:43)

• The Python Data Model

• A Guide to Python’s Magic Methods

• Expert Python Tutorial #2 - Dunder/Magic Methods & The Python Data Model

• Notebook on Datamodel

• Code examples from teachings

Exercises

Ex1: Deck of cards

Solution

Continue with the deck example and implement the

• __len__ method

• __add__ method

• __repr__ method

• __str__ method

• __setitem__ method

• __delitem__ method

We look at this together in a short while.

When you a done, take a look at the 2 exercises below and ask your questions.

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• Linked List

• Jelly Beans