This is an example for the library Fisica for Processing in Python.

CircleMutualAttraction

# Example created by Speykious

add_library('fisica')

world = FWorld()
def setup():
    size(1000, 600)
    smooth()
    frameRate(60)
    Fisica.init(this)
    global world
    world.setGravity(0, 0)

liobj = []
    
def draw():
    background(50)
    global liobj
    global world
    
    if frameCount%30==0 and frameCount<60**2:
        addObj()
        world.add(liobj[-1])
    attraction(1000)
    world.draw()
    world.step()
        
# The two next functions are based on the global liobj list
def addObj():
    global liobj
    obj = FCircle(random(5, 15))
    obj.setRestitution(0)
    obj.setFriction(0)
    obj.setPosition(random(100, width-100), random(100, height-100))
    liobj.append(obj)

def attraction(intensity):
    global liobj
    for o in liobj:
        for b in liobj:
            # An object has not to be attracted by himself
            if o!=b:
                opos = PVector(o.getX(), o.getY()) # object o's position
                bpos = PVector(b.getX(), b.getY()) # object b's position
                
                # the two vectors's difference:
                # the vector's end is on b
                bvect = PVector.sub(bpos, opos)
                
                # Force created from bvect
                force = PVector.div(bvect, bvect.mag()**2)
                force.mult(intensity)
                # Add force to object o
                o.addForce(force.x, force.y)