Объяснить код

#!/bin/env python
# -*- coding: utf-8 -*-
 
import sys
from copy import copy, deepcopy
 
def make_one(a, b, i):
    d = 1. / a[i][i]
 
    for k in range(len(a[i])):
        a[i][k] *= d
 
    b[i] *= d
    return a, b
 
def make_zero(a, b, i, j):
    n = len(a)
    m = len(a[0])
 
    for k in range(n):
        if k != i and a[k][j] == 1:
            break
 
    d = a[i][j]
 
    for l in range(m):
        a[i][l] -= a[k][l]*d
 
    b[i] -= b[k]*d
 
    return a, b
 
def solve(a, b):
    n = len(a)
    m = len(a[0])
 
    a = deepcopy(a); b = copy(b)
 
    for j in range(m):
        a, b = make_one(a, b, j)
        r = range(n); r.remove(j)
        for i in r:
            a, b = make_zero(a, b, i, j)
 
    return a, b
 
def input_data(argv):
    a = []; b = []
    b = argv[2].split(' ')
 
    m = len(b)
    b = [float(b[j]) for j in range(m)]
 
    t = argv[1].split(' ')
    n = len(t) / m
 
    k = 0
    for i in range(n):
        a.append([])
        for j in range(m):
            a[i].append(float(t[k]))
            k += 1
 
    return a, b
 
if __name__ == "__main__":
    if len(sys.argv) < 3:
        print("usage: %s '1 1 1 4 2 1 9 3 1' '0 1 3'" % sys.argv[0])
        sys.exit(1)
 
    a, b = input_data(sys.argv)
    a, b = solve(a, b)
    print(b)