This challenge write-up first appeared on PyBites.

There is nothing like a challenge to bring out the best in man. - Sean Connery

Hi Pythonistas, a new week, a new 'bite' of Python coding! This week we will let you experiment with Object Oriented Programming, an important skill and fundamental building block of (everthing-is-an-object) Python. Enjoy!

The Challenge

If you are new to OOP you might want to checkout our primer tutorial first.

Requirements:

• Define a class with a constructor (__init__ = object setup code, e.g. defining instance variables) and at least two methods. To relive PyCon you could have a generic Session class, but use any concept you like (Employee, Car, Person, Animal, Account, Notebook, etc).

• Define a subclass that inherits from the parent class. For example you could let (Lightning)Talk, KeyNote and Workshop be subclasses (inherit from) Session. Other examples: Employee - Manager / Developer, Car - Toyota, Account - SavingsAccount ... you get the idea.

• Define another class for use in the initial (sub)class. So for the PyCon Session example you could pull in a bunch of Person (Developer) objects that joined it. This Python OOP book has an example of a Notebook class to which Note objects are getting added. Or you could model a Blog with Posts, Tags, Categories, Comments. The possibilities are endless.

• Another (more fun) option that could be a good fit for OOP is developing a simple game with different Characters (Monsters, Heros, maybe Princesses even?) and Places they go, each class (blueprint) defining its own state (attributes) and behaviors (methods).

• We hope you follow along so far. For the more experienced coders among us, get bonus credits if you can:

  • apart from Inheritance implement Polymorphism and Encapsulation.

  • use one or more class and/or static methods. You could have a class variable keep track of the number of instances of the class for example.

  • investigate and use Abstract base classes (= ABCs, see also our OOP primer)

  • implement special (aka "dunder" aka "magic") methods which we covered here, at least __str__ and __repr__

    To get an idea of the difference between these two and a list of dunder methods on a typical Python object run this:

    >>> from datetime import datetime as dt 
    >>> d = dt.now()
    >>> str(d) 
    '2017-05-22 12:16:08.816364'
    >>> repr(d) 
    'datetime.datetime(2017, 5, 22, 12, 16, 8, 816364)'
    >>> help(d)
    

  • not sure if we should go down the route of multiple inheritance but it is possible if you have a use case. You can use __mro__ to figure out the inheritance order.

Getting ready

See our INSTALL doc how to fork our challenges repo to get cracking.

This doc also provides you with instructions how you can submit your code to our community branch via a Pull Request (PR). We will feature your PRs in our end-of-the-week challenge review (previous editions).

Feedback

If you have ideas for a future challenge or find any issues, please contact us or open a GH Issue.

Last but not least: there is no best solution, only learning more and better Python. Good luck!

Keep Calm and Code in Python!

-- Bob and Julian