Solve linear system in Python.

solve_linear

def minor(a, row, col):
    result = []
    for line in a[:row] + a[row+1:]:
        result.append(line[:col] + line[col+1:])
    return result

def determinant(a):
    if len(a) == 2:
        return a[0][0] * a[1][1] - a[1][0] * a[0][1]
    result = 0
    sign = 1
    for j in range(len(a)):
        result += sign * a[0][j] * determinant(minor(a, 0, j))
        sign = -sign
    return result

def replace_column(a, col, values):
    result = []
    for row, value in zip(a, values):
        result.append(row[:col] + [value] + row[col+1:])
    return result

def solve_linear_system(matrix, values):
    d = determinant(matrix)
    if d == 0:
        return None
    return [determinant(replace_column(matrix, i, values)) / d for i in range(4)]