In this blog post, I’m taking a game off of Pygame.org and going through it to make it more readable and extend its functionality. This is an intermediate level tutorial and assumes some familiarity with Python. This can be pretty helpful if you know programming basics but want to know, “How can I write better code?” (And because someone always brings it up, I have this disclaimer: Of course, these changes are my own subjective idea of “better” and not necessarily changes that another developer would make.)
Demon Kingdom by Logi540 is a defense game where monsters walk from the left side of the screen. The player needs to attack them by clicking on them, and can pick up gems to use for spells. If any monster reaches the right side of the screen, the player loses. Download source code.
The main theme of my changes is:
- Removing duplicate code. Duplicate code is bad because if you have to change it (to add features or fix bugs) you may forget to change it in every duplicated place.
- Remove magic numbers. Magic numbers are hard-coded integer values which are bad because they don’t describe what they represent. A better alternative is to use a constant instead (these are the ALL-CAPS variables).
- Put sequential variables in lists and use loops. Instead of having variables named like
spam3, and so on, it’s better to have a single list variable, and have a loop run code on each item in the list. This usually leads to a decrease in duplicate code.
- Get rid of unneeded variables. Removing code reaps tons of benefits: there’s less code a programmer has to read and understand, less code that a programmer has to look through when debugging, and less code (usually) means less bugs and “moving parts” that could break.
Here’s the inital check in of all the files. The file I’ll be modifying is named
demonkingdom_makeover.py. This program requires Pygame to be installed to run. I recommend downloading the game, playing it a couple times, and looking through the source code before continuing with this article. For each section, open up the diff link to see what the exact changes I made were.