Python/Pygame performance dump

This is a living document that I update from time to time containing the dos and don’ts to getting useable performance for your Pygame games. There’s some python stuff in here too but we’re mostly here for Pygame.

Before doing anything, you should grab a profiler and run it against your game. I personally use scalene.

Oh and a shameless plug before we begin, my game

Pygame

Convert your images, all of them
Don’t scale things in a loop. Do it outside (usually in the __init__)
Don’t blit to your display size, blit to your game’s resolution (320x180 in my case) and scale that up.
Don’t render text per frame. Do it in the __init__ and then reference it later
Alpha blitting is slower than non-alpha, beware of this
If you just care about if something has collided, use pygame.sprite.spritecollideany, it’s faster than spritecollide, it even mentions this in the docs
Use object pools to prevent creating loads of stuff on the fly. This is a bit more involved but there’s some good reading here. I use this successfully for my particle system.
Use a simple grid to speed up collisions. This is also slightly involved but it’s helped me quite a lot with optimising bullets in my game

The last two in particular I’d only pull out when you see a problem. Don’t optimise for the sake of optimising.

Python

Where building lists, dicts, sets etc, use comprehensions.

## Why? Comprehensions are at a C level so are always going to be faster than your `for` loop Don't do: ``` even_numbers = [] for i in range(10): if i % 2 == 0: even_numbers.append(i) ``` Do: ``` even_numbers = [i for i in range(10) if i % 2 == 0] ```

Anywhere you’re using dict() or list(), replace them with {} and [] respectively. Again, it’s faster
If the data in your list does not change, use a tuple. Again, faster