参考文献：https://github.com/xiantang/Spider/blob/master/Anti_Anti_Spider_521/pass_521.py
写在前面的话
Python在爬虫方面的优势，想必业界无人不知，随着互联网信息时代的的发展，Python爬虫日益突出的地位越来越明显，爬虫与反爬虫愈演愈烈。下面分析一例关于返回HTTP状态码为521的案例。
案例准备
- 案例网站：【中国一带一路官网】， 以抓取文章【“一带一路”建设成果图鉴丨陆海内外联动，湖北推动产能合作纵深推进】为例，进行深度剖析。
案例剖析
1） 浏览器访问【“一带一路”建设成果图鉴丨陆海内外联动，湖北推动产能合作纵深推进】：
python_anti_spider_521_url_yidaiyilu_20190505.png
2）写ython代码访问，查看http(s)返回状态
# coding:utf-8
import requests
from fake_useragent import UserAgent
USER_AGENT = UserAgent()
ua = USER_AGENT.random
url = r'https://www.yidaiyilu.gov.cn/xwzx/gnxw/87373.htm'
headers = {
"Host": "www.yidaiyilu.gov.cn",
"User-Agent": ua
}
rs = requests.session()
resp = rs.get(url)
print(resp.status_code)
print(resp.text)
不幸的是，返回的http的状态码却是501，text为一段混淆的js代码。
python_anti_spider_521_requests_20190505.png
3）百度查资料，推荐为文首的【参考文献】
继续参照资料修改代码，Python执行JS首选execjs，pip安装如下：
pip install PyExecJS
将请求到的js执行：
text_521 = ''.join(re.findall('<script>(.*?)</script>', resp.text))
func_return = text_521.replace('eval', 'return')
content = execjs.compile(func_return)
print(content.call('f'))
将返回的结果print发现还是一段JS，标准格式化（【格式化Javascript工具】），结果如下所示：
var _2i = function () {
setTimeout('location.href=location.pathname+location.search.replace(/[\?|&]captcha-challenge/,\'\')', 1500);
document.cookie = '__jsl_clearance=1557019601.296|0|' + (function () {
var _2i = [([(-~[] << -~[])] * (((+!+{}) + [(-~[] << -~[])] >> (-~[] << -~[]))) + []), (-~{} + [] + [
[]
][0]) + [3 - ~(+!+{}) - ~(+!+{})], (-~{} + [] + [
[]
][0]) + [5], (-~{} + [] + [
[]
][0]) + [~~''], (-~{} + [] + [
[]
][0]), [-~~~!{} + [~~
[]
] - (-~~~!{})], (-~{} + [] + [
[]
][0]) + [-~{} - ~[-~{} - ~{}]], (-~{} + [] + [
[]
][0]) + (-~{} + [] + [
[]
][0]), [-~(+!+{})], (-~{} + [] + [
[]
][0]) + ([(-~[] << -~[])] * (((+!+{}) + [(-~[] << -~[])] >> (-~[] << -~[]))) + []), (-~{} + [] + [
[]
][0]) + (-~[-~{} - ~{}] + [
[]
][0]), (((-~[] << -~[]) << (-~[] << -~[])) + [
[]
][0]), [3 - ~(+!+{}) - ~(+!+{})], (-~{} + [] + [
[]
][0]) + (((-~[] << -~[]) << (-~[] << -~[])) + [
[]
][0]), [5],
[-~{} - ~[-~{} - ~{}]], (-~{} + [] + [
[]
][0]) + [-~(+!+{})], (-~[-~{} - ~{}] + [
[]
][0]), [~~'']
],
_1d = Array(_2i.length);
for (var _5 = 0; _5 < _2i.length; _5++) {
_1d[_2i[_5]] = ['Bz', (-~[-~{} - ~{}] + [
[]
][0]), [{} + [] + [
[]
][0]][0].charAt(-~~~!{}), 'DR', ([(-~[] << -~[])] / (+!/!/) + [] + [
[]
][0]).charAt(-~[-~~~!{} - ~(-~[] - ~{} - ~{})]) + (+[(+!+{}), (+!+{})] + []).charAt((+!+{})), [
[][
[]
] + [] + [
[]
][0]
][0].charAt(-~{} - ~[-~{} - ~{}]), 'qM', (((-~[] << -~[]) << (-~[] << -~[])) + [
[]
][0]) + (+[(+!+{}), (+!+{})] + []).charAt((+!+{})) + (-~{}
/~~''+[]+[[]][0]).charAt((+!/!/)),'S','g%',(((-~[]<<-~[])<<(-~[]<<-~[]))+[[]][0]),'HxXL',[[][[]]+[]+[[]][0]][0].charAt(-~{}-~[-~{}-~{}]),'D',[-~(+!+{})],'T%','YW',[{}+[]+[[]][0]][0].charAt(-~~~!{}),'vw'][_5]};return _1d.join('')})()+';Expires=Sun, 05-May-19 02:26:41 GMT;Path=/;
'};if((function(){try{return !!window.addEventListener;}catch(e){return false;}})()){document.addEventListener('
DOMContentLoaded ',_2i,false)}else{document.attachEvent('
onreadystatechange ',_2i)}
4）修改与浏览器相关的代码，然后放入浏览器的console进行调试。
python_anti_spider_521_js_debug_20190505.png
注意，在调试过程中，不难发现，js变量是动态生成的。最初还嵌套有document.createElement('div')，Python的execjs包不支持处理这类代码，需要做相应处理。
5）综上分析，完整代码如下：
#!/usr/bin/env python
# coding:utf-8
import sys
import re
import requests
import execjs
from fake_useragent import UserAgent
reload(sys)
sys.setdefaultencoding('utf8')
class YiDaiYiLuSpider(object):
"""
中国一带一路网（521反爬）
"""
USER_AGENT = UserAgent()
ua = USER_AGENT.random
url = r'https://www.yidaiyilu.gov.cn/xwzx/gnxw/87373.htm'
headers = {
"Host": "www.yidaiyilu.gov.cn",
"User-Agent": ua
}
@classmethod
def get_text521(cls):
"""
:return:
"""
rs = requests.session()
resp = rs.get(url=cls.url, headers=cls.headers)
text_521 = ''.join(re.findall('<script>(.*?)</script>', resp.text))
cookie_id = '; '.join(['='.join(item) for item in resp.cookies.items()])
return cookie_id, text_521
@classmethod
def generate_cookies(cls, func):
"""
:param func:
:return:
"""
func_return = func.replace('eval', 'return')
content = execjs.compile(func_return)
eval_func = content.call('f')
var = str(eval_func.split('=')[0]).split(' ')[1]
rex = r">(.*?)</a>"
rex_var = re.findall(rex, eval_func)[0]
mode_func = eval_func.replace('document.cookie=', 'return ').replace(';if((function(){try{return !!window.addEventListener;}', ''). \
replace("catch(e){return false;}})()){document.addEventListener('DOMContentLoaded'," + var + ",false)}", ''). \
replace("else{document.attachEvent('onreadystatechange'," + var + ")}", '').\
replace(r"setTimeout('location.href=location.pathname+location.search.replace(/[\?|&]captcha-challenge/,\'\')',1500);", '').\
replace('return return', 'return').\
replace("document.createElement('div')", '"https://www.yidaiyilu.gov.cn/"').\
replace(r"{0}.innerHTML='<a href=\'/\'>{1}</a>';{0}={0}.firstChild.href;".format(var, rex_var), '')
content = execjs.compile(mode_func)
cookies_js = content.call(var)
__jsl_clearance = cookies_js.split(';')[0]
return __jsl_clearance
@classmethod
def crawler(cls):
"""
:return:
"""
url = r'https://www.yidaiyilu.gov.cn/zchj/sbwj/87255.htm'
cookie_id, text_521 = cls.get_text521()
__jsl_clearance = cls.generate_cookies(text_521)
cookies = "{0};{1};".format(cookie_id, __jsl_clearance)
cls.headers["Cookie"] = cookies
print(cls.headers)
res = requests.get(url=url, headers=cls.headers)
res.encoding = 'utf-8'
print(res.text)
if __name__ == '__main__':
YiDaiYiLuSpider.crawler()
运行结果如下：
python_anti_spider_521_js_result_20190505.png
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