#coding:utf-8
import random

class SymMat(object):

    def __init__(self, length=4):
        self.length = length
        self.matrix = [[0]*length]*length
        values = range(length*2)
        v = random.sample(values, length)
        pprint(self.matrix)
        print '------------before'
        self.matrix[1][0:] = v

        pprint(self.matrix)


def pprint(l):
    for i in l:
        print i

sm = SymMat(5)

输出：

[0, 0, 0, 0, 0]
[0, 0, 0, 0, 0]
[0, 0, 0, 0, 0]
[0, 0, 0, 0, 0]
[0, 0, 0, 0, 0]
------------before
[7, 9, 4, 3, 5]
[7, 9, 4, 3, 5]
[7, 9, 4, 3, 5]
[7, 9, 4, 3, 5]
[7, 9, 4, 3, 5]

仅对列表中第一行赋值，应该仅仅改变一行的,百思不解！ 问题已解决，* 赋值的时候是直接引用过去的，n个列表id相等~~