今天想下数据库系统概念里的实践习题答案，因为pdf有26个，写了个爬虫来下载，顺便学一下python

import urllib

for i in range(1, 26):
    url = r"http://codex.cs.yale.edu/avi/db-book/db6/practice-exer-dir/" + str(i) + "s.pdf"
    path = r"./"+str(i)+".pdf"
    data = urllib.urlopen(url).read()
    f = file(path,"wb")
    f.write(data)
    f.close()
    print "finish download " + url + "!"