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Object-oriented programming opens up a ton of new ways and ideas for us to use when creating software. That means it's time for us to start thinking about the design of our code.
- Keep your code as simple as possible
- Don't repeat yourself (DRY)
- Your code should have only the bells and whistles that it needs (YAGNI)
- Write Python like Python, not like any other language
This is a great time to familiar yourself with PEP 8 and PEP 20, two documents that most Python developers use to guide what their code looks like and how they think about code while creating it.
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So, before we get too far into
the mechanics of programming,
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let's talk about the biggest
subject of all design.
0:04
I don't mean how your software looks
on a website or a phone, though.
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I'm talking about the organization
thinking and layout of your code.
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In previous courses, most of our
code has been in a single file.
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This is fine for
small amounts of code, but
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you'll quickly see that we don't
always have small code footprints.
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Libraries and tools can quickly
reach hundreds, if not thousands,
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of lines of code.
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That's just not something you
want to read all in one file.
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We've all been there, right,
a document that just keeps scrolling and
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scrolling and scrolling.
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Now, imagine you're on line
595 of some script and
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see a function reference from
all the way up at line 18.
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IDEs and other editors can
reduce the amount of scrolling,
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but wouldn't it be better if
you didn't have to do that?
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And this is the first case
that software design solves.
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Well, it helps at least.
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We can break our code up into modules or
files.
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By putting code into logical groupings we
can make it easier to take it all in and
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think about what we need
to do to do our job.
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This logical grouping
goes even further though.
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We already grouped related lines
of code together into functions.
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Now with classes we have
another layer of grouping.
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If you have multiple functions that all
work together think about putting them
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into a class.
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OOP provides us with so many tools that
it's often hard to know which ones to use,
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or, if you should even use any of them.
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I don't want to just
dump a ton of terms and
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features on you, so, I'll be bringing
them up as we go through the course.
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I'll also be talking about how to use and
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think about these features in
the design of your software.
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But I can only influence your thinking so
far.
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I need you to also consider how
you'd use each of these things
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in the design of your own software.
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An often overlooked truth of software
development is that there's rarely any
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one correct way to solve a problem or
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design an algorithm, so like I said
this organization starts at its
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barest of bones with organizing
code into functions and classes.
1:45
Let's think back to the shopping list
app that we built in Python basics and
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Python collections.
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[SOUND] We had a list that held
the things we wanted to shop for,
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we had functions to add things to
the list, reorganize the list,
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and remove things we didn't need or
had already bought.
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Well right there I see something
that makes sense for a class,
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the ShoppingList itself.
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I can see going a step further though and
making each thing on the list and
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instance of some other class.
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Maybe this class would hold the name for
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the thing, how many that I wanted,
what store it was at, who knows.
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There are many options for
the functionality of this class.
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And that brings me to another point,
ruthless editing.
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As you build classes and
methods and functionality,
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keep in mind a very common acronym, YAGNI,
which stands for, you ain't gonna need it.
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Keep your code lean and mean and
you'll find it easier to use and
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better for building awesome things with.
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It's always a good idea to keep it
simple or as the Zen of Python says,
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if implementation is hard to explain, it's
a bad idea. Often you'll find that you can
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approach software design like you would
the design of something in the real world.
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Just like you wouldn't add a fish
radar to your screwdriver,
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you probably shouldn't add a function
to send email to your calculator app,
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practicality and logical thinking will
lead to better software every time.
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As part of that practicality, remember
you're writing Python not Java or C# or
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any other language.
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If you come to Python from one of those
languages, you might expect me to talk
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about getters and setters or
access controls on methods and attributes.
3:04
Python doesn't rely on
these design features.
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And you'll rarely find a place where
they're absolutely needed in Python.
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Stick to writing simple, clean code and
as little code as possible,
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and you'll find yourself
a happier programmer.
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All right, I think that's enough
talking about design for now.
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Go back and look at the code we've
written together previously and
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see if you can find places
to add simple classes.
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Even if you can't add them right now,
keep those places in mind for
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when you hit further through this course.
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I'm sure you'll find all sorts of
places to improve our old code.
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Now though,
let's get into the fun stuff and
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start talking about the real wealth of
object oriented design, inheritance.
3:36
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