Circle Collisions  2.0.0
A Circle to Circle collision detection algorithm.
Ian Mallett
(geometrian)
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Circle Collisions 2.0.0 — 3 Feb, 2008
Pygame.org account Comments

Idteller 20111015 06:09:07
Nice code. I recommend defining your screen, or surface as stated below;
SCREEN_WIDTH = 800SCREEN_HEIGHT = 600SCREEN_HEIGHT = 600screen = pygame.display.set_mode((SCREEN_WIDTH,SCREEN_HEIGHT))
Then whenever you refer to the screen height or width you can do so by entering;
screen.get_width() or screen.get_height()This will allow you to modify the screen size if necessary without browsing through code for all screen width and height values. Instead you can just change the screen size at the beginning. 
Patric 20140724 12:35:09
I had a look at your collision code and I wondered a bit about this part here in the CollisionDetect() function:
if Circle != Circle2:
Aren't you actually checking the circles with lower indices twice with this approach? My approach in a small game I recently wrote, was to go by the indices of the circles:
for n in range(len(Circles)):
# The whole code before the collision detection
if n < len(Circles)  1:
if Circles[n].radius + Circles[n + 1].radius < math.hypot(Circles[n].x  Circles[n + 1].x, Circles[n].y  Circles[n + 1].y):
CircleCollide(Circles[n], Circles[n + 1])What are your thoughts on this?
Pat

Named Tuple 20140725 14:17:24
I think he is checking the same circle pairs twice. Going by the indices works, but I think your approach misses nonadjacent circles in the list, i.e. circle 1 and circle 3 won't be checked. A solution is to use the python itertools library as below:
import itertools
for circle1, circle2 in itertools.combinations(range(20), 2):
#check for circle collision
# if circle collision:
# update circle velocityHope this helps! I am making something like this as well right now, maybe I will upload it at some point.

hanna hansen 20200424 18:47:18.951015
I really liked your code! in your function collision_detection you've written : Xdiff =(C1.xC2.x) and Ydiff = (C1.yC2.y). What is the purpose of minus() in front of the paranthesis?