import random

def zero_matrix(size):
    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):
    m = []
    
    for i in range(size):
        m.append([0] * size)
    
    return m

def random_matrix(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):
    for i in range(len(m)):
        print m[i]
        
def identity(size):
    m = zero_matrix(size)
    
    for i in range(size):
        m[i][i] = 1
    
    return m

def matrix_sum(m):
    total = 0
    
    for row in range(len(m)):
        for col in range(len(m[row])):
            total += m[row][col]
            
    return total