尝试用Python实现邻接表。但是发现报错：

import queue

class node(object):
    def __init__(self, u, v, w, next):
        self.u = u
        self.v = v
        self.w = w
        self.next = next


head = [0 for i in range(3000)]
t = [node(0, 0, 0, 0) for i in range(int(1e6))]

bian = 0
def addedge(u, v, w):
    global bian
    global t
    global head
    bian += 1
    t[bian] = node(u, v, w, head[u])
    head[u] = bian

报错：