流程
1. post
根据思路里的第一步，我们首先需要用 post 方式取到加密后的js字段，笔者使用了 requests第三方库来执行，关于爬虫可以参考 我之前的文章
i. 先把post中的headers格式化
# set the headers or the website will not return information
# the cookies in here you may need to change
headers = {
"cache-Control": "no-cache",
"accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,"
"*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
"accept-encoding": "gzip, deflate, br",
"accept-language": "zh-CN,zh;q=0.9,en;q=0.8",
"content-type": "application/x-www-form-urlencoded",
"cookie": "lang=en; country=CN; uid=fd94a82a406a8dd4; sfHelperDist=72; reference=14; "
"clickads-e2=90; poropellerAdsPush-e=63; promoBlock=64; helperWidget=92; "
"helperBanner=42; framelessHdConverter=68; inpagePush2=68; popupInOutput=9; "
"_ga=GA1.2.799702638.1610248969; _gid=GA1.2.628904587.1610248969; "
"PHPSESSID=030393eb0776d20d0975f99b523a70d4; x-requested-with=; "
"PHPSESSUD=islilfjn5alth33j9j8glj9776; _gat_helperWidget=1; _gat_inpagePush2=1",
"origin": "https://en.savefrom.net",
"pragma": "no-cache",
"referer": "https://en.savefrom.net/1-youtube-video-downloader-4/",
"sec-ch-ua": "\"Google Chrome\";v=\"87\", \"Not;A Brand\";v=\"99\",\"Chromium\";v=\"87\"",
"sec-ch-ua-mobile": "?0",
"sec-fetch-dest": "iframe",
"sec-fetch-mode": "navigate",
"sec-fetch-site": "same-origin",
"sec-fetch-user": "?1",
"upgrade-insecure-requests": "1",
"user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) "
"Chrome/87.0.4280.88 Safari/537.36"}
其中 cookie 部分可能要改，然后最好以你们浏览器上的为主，具体每个参数的含义不是本文范围，可以自行去搜索引擎搜
ii.然后把参数也格式化
# set the parameter, we can get from chrome
kv = {"sf_url": url,
"sf_submit": "",
"new": "1",
"lang": "en",
"app": "",
"country": "cn",
"os": "Windows",
"browser": "Chrome"}
其中 sf_url 字段是我们要下载的youtube视频的url，其他参数都不变
iii. 最后再执行 requests 库的post请求
# do the POST request
r = requests.post(url="https://en.savefrom.net/savefrom.php", headers=headers,
data=kv)
r.raise_for_status()
注意是 data=kv
iv. 封装成一个函数
import requests
def gethtml(url):
# set the headers or the website will not return information
# the cookies in here you may need to change
headers = {
"cache-Control": "no-cache",
"accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,"
"*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
"accept-encoding": "gzip, deflate, br",
"accept-language": "zh-CN,zh;q=0.9,en;q=0.8",
"content-type": "application/x-www-form-urlencoded",
"cookie": "lang=en; country=CN; uid=fd94a82a406a8dd4; sfHelperDist=72; reference=14; "
"clickads-e2=90; poropellerAdsPush-e=63; promoBlock=64; helperWidget=92; "
"helperBanner=42; framelessHdConverter=68; inpagePush2=68; popupInOutput=9; "
"_ga=GA1.2.799702638.1610248969; _gid=GA1.2.628904587.1610248969; "
"PHPSESSID=030393eb0776d20d0975f99b523a70d4; x-requested-with=; "
"PHPSESSUD=islilfjn5alth33j9j8glj9776; _gat_helperWidget=1; _gat_inpagePush2=1",
"origin": "https://en.savefrom.net",
"pragma": "no-cache",
"referer": "https://en.savefrom.net/1-youtube-video-downloader-4/",
"sec-ch-ua": "\"Google Chrome\";v=\"87\", \"Not;A Brand\";v=\"99\",\"Chromium\";v=\"87\"",
"sec-ch-ua-mobile": "?0",
"sec-fetch-dest": "iframe",
"sec-fetch-mode": "navigate",
"sec-fetch-site": "same-origin",
"sec-fetch-user": "?1",
"upgrade-insecure-requests": "1",
"user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) "
"Chrome/87.0.4280.88 Safari/537.36"}
# set the parameter, we can get from chrome
kv = {"sf_url": url,
"sf_submit": "",
"new": "1",
"lang": "en",
"app": "",
"country": "cn",
"os": "Windows",
"browser": "Chrome"}
# do the POST request
r = requests.post(url="https://en.savefrom.net/savefrom.php", headers=headers,
data=kv)
r.raise_for_status()
# get the result
return r.text
2. 调用解密函数
i. 分析
这其中的难点在于在python里执行javascript代码，而晚上的解决方法有 PyV8 等，本文选用 execjs 。在思路部分我们可以发现js部分的最后几行是解密函数，所以我们只需要在 execjs 中先执行一遍全部，然后再单独执行解密函数就好了
ii. 先取出js部分
# target(youtube address) url
url = "https://www.youtube.com/watch?v=YPvtz1lHRiw"
# get the target text
reo = gethtml(url)
# Remove the code from the head and tail (we need the javascript part, information store with encryption in js part)
reo = reo.split("<script type=\"text/javascript\">")[1].split("</script>")[0]
这里其实可以用正则，不过由于笔者正则表达式还不太熟练就直接用 split 了
iii. 取第一个解密函数作为我们用的解密函数
当你多取几次不同视频的结果，你就会发现每次的解密函数都不一样，不过位置都是还是在固定行数
# split each line(help us find the decrypt function in last few line)
reA = reo.split("\n")
# get the depcrypt function
name = reA[len(reA) - 3].split(";")[0] + ";"
所以 name 就是我们的解密函数了(变量名没取太好hhh)
iv. 用execjs执行
# use execjs to execute the js code, and the cwd is the result of `npm root -g`(the path of npm in your computer)
ct = execjs.compile(reo)
# do the decryption
text = ct.eval(name.split("=")[1].replace(";", ""))
其中只取 = 后面的和去掉分号是指指执行这个函数而不用赋值，当先执行赋值+解密然后取值也不是不可以
但是我们可以发现马上就报错了(要是有这么简单就好了)
1. this也就是window变量不存在
如果没记错是报错 this 或者 $b ，笔者尝试把全部 this 去掉或者把全部框在一个 class 里面(这样子this就变成那个class了)不过都没有成功，然后发现在 npm 下有个 jsdom 可以在 execjs 里模拟window变量(其实应该有更好方法的)，所以我们需要下载 npm 和里面的 jsdom ，然后改写以上代码
addition = """
const jsdom = require("jsdom");
const { JSDOM } = jsdom;
const dom = new JSDOM(`<!DOCTYPE html><p>Hello world</p>`);
window = dom.window;
document = window.document;
XMLHttpRequest = window.XMLHttpRequest;
"""
# use execjs to execute the js code, and the cwd is the result of `npm root -g`(the path of npm in your computer)
ct = execjs.compile(addition + reo, cwd=r'C:\Users\xxx\AppData\Roaming\npm\node_modules')
其中
- cwd 字段是 npm root -g 的结果，也就是npm的modules路径
- addition 是用来模拟 window 的
但是我们又可以发现下一个错误
2. alert不存在
这个错误是因为在 execjs 下执行 alert 函数是没有意义的，因为我们没有浏览器让他弹窗，且原本 alert 函数的定义是来源 window 而我们自定义了 window ，所以我们要在代码前重写覆盖 alert 函数(相当于定义一个alert)
# override the alert function, because in the code there has one place using
# and we cannot do the alerting in execjs(it is meaningless) however, if we donnot override, the code will raise a error
reo = reo.replace("(function(){", "(function(){\nthis.alert=function(){};")
v. 整合代码
# target(youtube address) url
url = "https://www.youtube.com/watch?v=YPvtz1lHRiw"
# get the target text
reo = gethtml(url)
# Remove the code from the head and tail (we need the javascript part, information store with encryption in js part)
reo = reo.split("<script type=\"text/javascript\">")[1].split("</script>")[0]
# override the alert function, because in the code there has one place using
# and we cannot do the alerting in execjs(it is meaningless) however, if we donnot override, the code will raise a error
reo = reo.replace("(function(){", "(function(){\nthis.alert=function(){};")
# split each line(help us find the decrypt function in last few line)
reA = reo.split("\n")
# get the depcrypt function
name = reA[len(reA) - 3].split(";")[0] + ";"
# add jsdom into the execjs because the code will use(maybe there is a solution without jsdom, but i have no idea)
addition = """
const jsdom = require("jsdom");
const { JSDOM } = jsdom;
const dom = new JSDOM(`<!DOCTYPE html><p>Hello world</p>`);
window = dom.window;
document = window.document;
XMLHttpRequest = window.XMLHttpRequest;
"""
# use execjs to execute the js code, and the cwd is the result of `npm root -g`(the path of npm in your computer)
ct = execjs.compile(addition + reo, cwd=r'C:\Users\19308\AppData\Roaming\npm\node_modules')
# do the decryption
text = ct.eval(name.split("=")[1].replace(";", ""))
3. 分析解密结果
i. 取关键json
运行完上面的部分，解密结果就存在text里了，而我们在思路中可以发现，真正对我们重要的就是存在 window.parent.sf.videoResult.show() 里的json，所以用正则表达式取这一部分的json
# get the result in json
result = re.search('show\((.*?)\);;', text, re.I | re.M).group(0).replace("show(", "").replace(");;", "")
ii. 格式化json
python可以格式化json的库有很多，这里笔者用了 json 库(记得import)
# use `json` to load json
j = json.loads(result)
iii. 取下载地址
接下来就到了最后一步，根据思路里和json格式化工具我们可以发现 j["url"][num]["url"] 就是下载链接，而 num 是我们要的视频格式(不同分辨率和类型)
# the selection of video(in this case, num=1 mean the video is
# - 360p known from j["url"][num]["quality"]
# - MP4 known from j["url"][num]["type"]
# - audio known from j["url"][num]["audio"]
num = 1
downurl = j["url"][num]["url"]
# do some download
# thanks :)
# - EOF -
3. 全部代码
# -*- coding: utf-8 -*-
# @Time: 2021/1/10
# @Author: Eritque arcus
# @File: Youtube.py
# @License: MIT
# @Environment:
# - windows 10
# - python 3.6.2
# @Dependence:
# - jsdom in npm(windows also can use)
# - requests, execjs, re, json in python
import requests
import execjs
import re
import json
def gethtml(url):
# set the headers or the website will not return information
# the cookies in here you may need to change
headers = {
"cache-Control": "no-cache",
"accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,"
"*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",
"accept-encoding": "gzip, deflate, br",
"accept-language": "zh-CN,zh;q=0.9,en;q=0.8",
"content-type": "application/x-www-form-urlencoded",
"cookie": "lang=en; country=CN; uid=fd94a82a406a8dd4; sfHelperDist=72; reference=14; "
"clickads-e2=90; poropellerAdsPush-e=63; promoBlock=64; helperWidget=92; "
"helperBanner=42; framelessHdConverter=68; inpagePush2=68; popupInOutput=9; "
"_ga=GA1.2.799702638.1610248969; _gid=GA1.2.628904587.1610248969; "
"PHPSESSID=030393eb0776d20d0975f99b523a70d4; x-requested-with=; "
"PHPSESSUD=islilfjn5alth33j9j8glj9776; _gat_helperWidget=1; _gat_inpagePush2=1",
"origin": "https://en.savefrom.net",
"pragma": "no-cache",
"referer": "https://en.savefrom.net/1-youtube-video-downloader-4/",
"sec-ch-ua": "\"Google Chrome\";v=\"87\", \"Not;A Brand\";v=\"99\",\"Chromium\";v=\"87\"",
"sec-ch-ua-mobile": "?0",
"sec-fetch-dest": "iframe",
"sec-fetch-mode": "navigate",
"sec-fetch-site": "same-origin",
"sec-fetch-user": "?1",
"upgrade-insecure-requests": "1",
"user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) "
"Chrome/87.0.4280.88 Safari/537.36"}
# set the parameter, we can get from chrome
kv = {"sf_url": url,
"sf_submit": "",
"new": "1",
"lang": "en",
"app": "",
"country": "cn",
"os": "Windows",
"browser": "Chrome"}
# do the POST request
r = requests.post(url="https://en.savefrom.net/savefrom.php", headers=headers,
data=kv)
r.raise_for_status()
# get the result
return r.text
if __name__ == '__main__':
# target(youtube address) url
url = "https://www.youtube.com/watch?v=YPvtz1lHRiw"
# get the target text
reo = gethtml(url)
# Remove the code from the head and tail (we need the javascript part, information store with encryption in js part)
reo = reo.split("<script type=\"text/javascript\">")[1].split("</script>")[0]
# override the alert function, because in the code there has one place using
# and we cannot do the alerting in execjs(it is meaningless) however, if we donnot override, the code will raise a error
reo = reo.replace("(function(){", "(function(){\nthis.alert=function(){};")
# split each line(help us find the decrypt function in last few line)
reA = reo.split("\n")
# get the depcrypt function
name = reA[len(reA) - 3].split(";")[0] + ";"
# add jsdom into the execjs because the code will use(maybe there is a solution without jsdom, but i have no idea)
addition = """
const jsdom = require("jsdom");
const { JSDOM } = jsdom;
const dom = new JSDOM(`<!DOCTYPE html><p>Hello world</p>`);
window = dom.window;
document = window.document;
XMLHttpRequest = window.XMLHttpRequest;
"""
# use execjs to execute the js code, and the cwd is the result of `npm root -g`(the path of npm in your computer)
ct = execjs.compile(addition + reo, cwd=r'C:\Users\19308\AppData\Roaming\npm\node_modules')
# do the decryption
text = ct.eval(name.split("=")[1].replace(";", ""))
# get the result in json
result = re.search('show\((.*?)\);;', text, re.I | re.M).group(0).replace("show(", "").replace(");;", "")
# use `json` to load json
j = json.loads(result)
# the selection of video(in this case, num=1 mean the video is
# - 360p known from j["url"][num]["quality"]
# - MP4 known from j["url"][num]["type"]
# - audio known from j["url"][num]["audio"]
num = 1
downurl = j["url"][num]["url"]
# do some download
# thanks :)
# - EOF -
- 总计102行
近期有很多朋友通过私信咨询有关Python学习问题。为便于交流，点击蓝色自己加入讨论解答资源基地
- 开发环境
# @Environment:
# - windows 10
# - python 3.6.2
- 依赖
# @Dependence:
# - jsdom in npm(windows also can use)
# - requests, execjs, re, json in python
-end-
For 爬虫
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
本文作者: https://www.cnblogs.com/Eritque-arcus/ 或 https://blog.youkuaiyun.com/qq_40832960
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