python: "too many values to unpack" ?报错

代码：

__author__ = 'Kevin'

import random
rawdata = open("D:/recommend/ml-100k/u.data")

def SplitData(data, M, k, seed) :
    test = []
    train = []
    random.seed(seed)
    for user, item in data :
        if random.randint(0,M) == k:
            test.append([user,item])
        else:
            train.append([user,item])
    return train, test

if __name__ == "__main__":
    SplitData(rawdata,8,5,4)

这个数据集是Movielens里100000份电影评分数据，报错如下，请问怎么解决？：

C:\Python27\python.exe D:/recommend/read.py
Traceback (most recent call last):
  File "D:/recommend/read.py", line 18, in <module>
    SplitData(rawdata,8,5,4)
  File "D:/recommend/read.py", line 10, in SplitData
    for user, item in data :
ValueError: too many values to unpack

u.data前几行数据如下：