"""
Demonstrates how to implement and work with matrices
"""

import random


def zero_matrix(size):
    """
    Returns a size x size matrix of zeros
    :param size: (int) the size of the matrix
    :return: (list) the matrix of zeros
    """
    m = []

    for i in range(size):
        row_list = []

        for j in range(size):
            row_list.append(0)

        m.append(row_list)

    return m


def zero_matrix2(size):
    """
    An alternative implementation
    Returns a size x size matrix of zeros
    :param size: (int) the size of the matrix
    :return: (list) the matrix of zeros
    """
    m = []

    for i in range(size):
        m.append([0] * size)

    return m


def random_matrix(size):
    """
    Returns a size x size matrix of random numbers between 0 and size*size
    :param size: (int) the size of the matrix
    :return: (list) the matrix of random numbers in [0, size*size]
    """
    m = []

    for i in range(size):
        row_list = []

        for j in range(size):
            row_list.append(random.randint(0, size * size))

        m.append(row_list)

    return m


def print_matrix(m):
    """
    Prints the contents of the matrix m
    :param m: (list) the matrix to print
    :return: (None)
    """
    for row in m:
        print(row)


def print_matrix2(m):
    """
    An alternative implementation
    Prints the contents of the matrix m
    :param m: (list) the matrix to print
    :return: (None)
    """
    for row_number in range(len(m)):
        print(m[row_number])


def identity(size):
    """
    Returns an identity size x size matrix
    (zeros everywhere and ones on the diagonal)
    :param size: (int) the size of the matrix
    :return: (list) the identity matrix
    """
    m = zero_matrix(size)

    for i in range(size):
        m[i][i] = 1

    return m


def matrix_sum(m):
    """
    Returns the sum of the contents of the matrix m
    :param m: (list) the matrix to sum its contents
    :return: (int) the sum of the contents of matrix m
    """
    total = 0

    for r in range(len(m)):
        for c in range(len(m[r])):
            total += m[r][c]

    return total


def matrix_sum2(m):
    """
    Alternative implementation
    Returns the sum of the contents of the matrix m
    :param m: (list) the matrix to sum its contents
    :return: (int) the sum of the contents of matrix m
    """
    total = 0

    for row in m:
        for value in row:
            total += value

    return total


def matrix_sum3(m):
    """
    Alternative implementation
    Returns the sum of the contents of the matrix m
    :param m: (list) the matrix to sum its contents
    :return: (int) the sum of the contents of matrix m
    """
    total = 0

    for row_number in range(len(m)):
        total += sum(m[row_number])

    return total


def matrix_sum4(m):
    """
    Alternative implementation
    Returns the sum of the contents of the matrix m
    :param m: (list) the matrix to sum its contents
    :return: (int) the sum of the contents of matrix m
    """
    total = 0

    for row in m:
        total += sum(row)

    return total