列表通过＆＃34;参考＆＃34;即使在Python中使用list（）构造函数

Question

我正在尝试实施Karger的算法，并且在使用Python中的列表时遇到了麻烦。

我有一个输入列表input_v，它应该在整个程序中保持静态。在while循环中，我使用名为max_iters的{​​{1}}列表副本进行input_v迭代的Karger算法。在内部for循环的1次迭代结束时，似乎我在vertices上应用的所有逻辑也应用于vertices，即使我做input_v。

vertices = list(input_v)

这是在第二次迭代开始后的输出。

input_v = [[[1], 2, 3, 4], [[2], 1, 4], [[3], 1, 4], [[4], 2, 3]]

# Perform Karger's n^2ln(n) times to ensure p > 1-1/n
for i in range(0, max_iters):

    vertices = list(input_v)
    print 'new loop'
    print vertices
    print input_v

    #Contract edges n-2 times to find A and B
    for j in range(0, n - 2):

        # length of current array
        len_arr = n - j

        #rand_vn => random index within current array
        #i_vn => true index of vertex from orig array

        # Randomly select 1st vertex (v1) to contract
        rand_v1 = randint(1, len_arr) - 1
        i_v1 = vertices[rand_v1][0][0]

        # Randomly select 2nd vertex (v2) connected to v1
        i_in_v1 = randint(1,len(vertices[rand_v1]) - 1)
        i_v2 = vertices[rand_v1][i_in_v1]

        for k in range(0, len_arr):
            if i_v2 in vertices[k][0]:
                rand_v2 = k

        for y in vertices[rand_v2][1:]:
            if y not in vertices[rand_v1]:
                vertices[rand_v1].append(y);

        # Remove each other's indices from list of edges
        for q in vertices[rand_v2][0]:
            if q in vertices[rand_v1]:
                vertices[rand_v1].remove(q)
            # Add indices from v2 to v1 (supernode)
            vertices[rand_v1][0].append(q)

        for r in vertices[rand_v1][0]:
            if r in vertices[rand_v1]:
                vertices[rand_v1].remove(r)

        vertices.pop(rand_v2)

        print vertices

    del vertices[:]