How to set up a proxy for Python crawler

Some websites will have corresponding anti-crawler measures. For example, many websites will detect the number of visits to a certain IP in a certain period of time. If the frequency of visits is too fast and does not look like a normal visitor, it may ban the IP. Access. So we need to set up some proxy servers and change the proxy every once in a while. Even if the IP is banned, you can still change the IP and continue crawling.

In Python, you can use the ProxyHandler in urllib2 to set up a proxy server. The following code explains how to use the proxy:

import urllib2
# 构建了两个代理Handler，一个有代理IP，一个没有代理IP
httpproxy_handler = urllib2.ProxyHandler({"http" : "124.88.67.81:80"})
nullproxy_handler = urllib2.ProxyHandler({})
#定义一个代理开关
proxySwitch = True 
# 通过 urllib2.build_opener()方法使用这些代理Handler对象，创建自定义opener对象
# 根据代理开关是否打开，使用不同的代理模式
if proxySwitch:  
    opener = urllib2.build_opener(httpproxy_handler)
else:
    opener = urllib2.build_opener(nullproxy_handler)
request = urllib2.Request("http://www.baidu.com/")
# 使用opener.open()方法发送请求才使用自定义的代理，而urlopen()则不使用自定义代理。
response = opener.open(request)
# 就是将opener应用到全局，之后所有的，不管是opener.open()还是urlopen() 发送请求，都将使用自定义代理。
# urllib2.install_opener(opener)
# response = urlopen(request)
print response.read()

Used above It is a free open proxy. We can collect these free proxies on some proxy websites. If it can be used after testing, we will collect it and use it on the crawler.

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If you have enough proxies, you can put them in a list and randomly select a proxy to access the website. As follows:

import urllib2
import random
proxy_list = [
    {"http" : "124.88.67.81:80"},
    {"http" : "124.88.67.81:80"},
    {"http" : "124.88.67.81:80"},
    {"http" : "124.88.67.81:80"},
    {"http" : "124.88.67.81:80"}
]
# 随机选择一个代理
proxy = random.choice(proxy_list)
# 使用选择的代理构建代理处理器对象
httpproxy_handler = urllib2.ProxyHandler(proxy)
opener = urllib2.build_opener(httpproxy_handler)
request = urllib2.Request("http://www.baidu.com/")
response = opener.open(request)
print response.read()

The above are all free proxies, which are not very stable and often cannot be used. At this time, you can consider using a private proxy. That is to say, purchase an agent from an agent supplier. The supplier will provide a valid agent with its own username and password. The specific use is the same as that of a free agent. This is an additional account authentication, as follows:

# 构建具有一个私密代理IP的Handler，其中user为账户，passwd为密码
httpproxy_handler = urllib2.ProxyHandler({"http" : "user：passwd@124.88.67.81:80"})

The above is The method of setting up a proxy using urllib2 seems a bit troublesome. Let's take a look at how to use reqursts to use the proxy.

Use free proxy:

import requests
# 如果代理需要使用HTTP Basic Auth，可以使用下面这种格式：
proxy = { "http": "mr_mao_hacker:sffqry9r@61.158.163.130:16816" }
response = requests.get("http://www.baidu.com", proxies = proxy)
print response.text

Note: You can write the account password into the environment variable to avoid leakage

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