Graphics/animation:
anim.py      (simple animation holding classes)
asciiart.py  (creating animations defined in text file, can be usefull for prototyping)
graphics.txt (sample data)

Random terrain generation:
gen_terrain.py (using primitive Perlin noise implementation)

Random/Procedural generation:
markov.py (using Markov's chains to make strings)
spiro.py  (spirograph primitive experiment)

Pathfinding:
path_breadth.py (greedy search)

Weird experiments:
models.py


Stand-alone game programming examples:
01-sprite.py         Hello, World: init Pygame, create and display sprite
02-moving-sprite.py  Wandering Hobo: control the sprite
03-collisions.py     Kill All Humans: multiple enemies and collisions
04-encapsulating.py  Divide Et Impera: same as 03, but reorganized using classes + improved game loop timing
05-behaviour.py      Nemesis Entering: advanced behaviour

See https://www.pygame.org/docs/