# Author: Alex Gezerlis

# Numerical Methods in Physics with Python (CUP, 2020)

from kahansum import kahansum

from math import sqrt

def chargearray(nvals):

vals = [-0.5 + i/(nvals-1) for i in range(nvals)]

qtopos = {}

for i,posx in enumerate(vals):

for j,posy in enumerate(vals):

count = j + nvals*i + 1

key = 1.02*count if (i+j)%2==0 else -count

qtopos[key] = posx, posy

return qtopos

def vecmag(rs):

sq = [r**2 for r in rs]

return sqrt(kahansum(sq))

def fullpot(qtopos,rs):

potvals = []

for q,pos in qtopos.items():

diffs = [r - po for r,po in zip(rs,pos)]

R = vecmag(diffs)

potvals.append(q/R)

return kahansum(potvals)

if __name__ == '__main__':

qtopos = chargearray(6)

for y in 1,-1:

rs = [0.,y]

potval = fullpot(qtopos,rs)

print(rs, potval)