python 将数据随机分为训练集和测试集

# -*- coding: utf-8 -*-
"""
Created on Tue Jun 23 15:24:19 2015

@author: hd
"""

from sklearn import cross_validation

c = []
j=0
filename = r'C:UsershdDesktopookmarksookmarks.arff' 
out_train = open(r'C:UsershdDesktopookmarks	rain.arff','w')
out_test = open(r'C:UsershdDesktopookmarks	est.arff','w')

for line in open(filename):
#    items = line.strip().split()
    c.append(line)
 
c_train,c_test = cross_validation.train_test_split(c,test_size = 0.6)
for i in c_train:
    out_train.write(i)
for i in c_test:
    out_test.write(i)