Soma Matriz Interna

# coding: utf-8
# Programacao 1, 2014.1 Pedro Paulo
# Soma Matriz Interna

def soma_matriz_interna(M, ini, fim):
    soma = 0
    for i in range(M):
        for j, col in enumerate(M):
            if i >= ini[0] and i <= fim[0] and j >= ini[1] and j <= fim[1]:
                soma += M[i][j]
    return soma