我有两个函数可以用来创建一个数组:
    def makelist(size):
        list = []
        for i in range(size):
            list = list + [None]
        return list
    def mmatrix(rows,cols):
        matrix = makelist(rows)
        for i in range(rows):
            matrix[i] = makelist(cols)
        return matrix
当我创建一个数组:mmatrix(3,3))时,它会在同一行打印所有三个数组。如何在数组之间插入新行?