初试Python爬虫下载pdf

最近刚学完Boyd的Convex Optimization，真是对Boyd神佩服得五体投地。在他的lecture slides末尾发现原来还有进阶课程Stanford的ee364b，那本convex optimization只包括了ee364a，然而ee364b没有现成的完整slides一次性下载，只好写个爬虫挨个下载保存slides，在ee364b里的内容更加专业深入，估计实际很少用到。然后我把爬虫的代码贴上来，还好他们的网页结构比较简单，代码量不大。下载好的文件里有些是空白的，回网站一查发现确实是他们没有在里面留东西，就这样吧。

import requests
import re
import os
from bs4 import BeautifulSoup

def GetPage(url):
    page = requests.get(url)
    html = page.text
    return html

def GetList(html):
    soup = BeautifulSoup(html, "html5lib")
    list = soup.find_all(href=re.compile("lectures/"))
    pdfs = []
    for li in list:
        if (li.get('href'))[-4:] == ".pdf":
            pdfs.append(li.get('href'))
    return pdfs
    
def DownloadPdf(pdf,root_url):
    path = "C:/Users/Downloads/cvx/" + pdf[9:]
    urls = root_url + pdf
    r = requests.get(urls)
    f = open(path, "wb")
    f.write(r.content)
    f.close()
    return urls

url = "https://web.stanford.edu/class/ee364b/lectures.html"
root_url = "https://web.stanford.edu/class/ee364b/"
#print(GetList(GetPage(url)))
pdfs = GetList(GetPage(url))
for pdf in pdfs:
    print("Download finished: "+DownloadPdf(pdf, root_url))

还有计划把Standford的cs224n的lecture slides下载下来慢慢看，就在这个代码的基础上改吧