Python Web Crawling Tutorial: Practical Case Studies

First, why is your crawler always blocked? First understand the pit

Recently, a friend who does e-commerce complained to me that the price monitoring script he wrote in Python ran for two days and then went out of business. I took a look at the logs and I was happy - this buddy has been using the same IP to request the target site, it's strange that people don't block him! This is the time to bring out our saviorproxy IPThe Proxy IP is like putting a million masks on a crawler. Simply put, proxy IPs are like putting a million masks on a crawler to make the site think it's a different person on each visit.

Let's take an example: you want to go to the supermarket to try to eat, if you try to eat 20 times in a row and still do not buy, the security guard will certainly blow you away. But if you change into different clothes every time you go in, won't you be able to eat a few more rounds? Proxy IP is this "dress-up technique", but here the change is a network identity.

Second, hand to teach you to use ipipgo agent real capture

First the whole point of practical, let's use ipipgo's free package to do a demonstration. Suppose we want to capture the product information of an e-commerce platform, the key is torotating IPrespond in singingControl frequencyThe

import requests
from itertools import cycle

 从ipipgo获取的代理列表
proxies = [
    "http://user:pass@gateway.ipipgo.com:1000",
    "http://user:pass@gateway.ipipgo.com:1001",
     ...更多代理节点
]
proxy_pool = cycle(proxies)

url = "https://目标网站.com/product/123"

for _ in range(10):
    try:
         每次换代理
        proxy = next(proxy_pool)
        response = requests.get(url, proxies={"http": proxy}, timeout=5)
        print(response.text)
         建议加上2-5秒
    except Exception as e:
        print(f"用{proxy}出错啦:", str(e))

Note that there are two pits to avoid here: 1. Don't use free proxies (slow and unsafe) 2. Remember to add timeout settings. I recommend going directly toipipgo's commercial packagesThe response time of their home exclusive line can be controlled within 200ms.

Proxy IP use in the five must-know skills

A few practical lessons based on the mines I've stepped on over the years:

Particular emphasis is placed onrequest header masquerading asThis matter, many newbies think that changing the IP is all right, in fact, User-Agent, Referer, these parameters are not set up, minutes to expose the identity of the robot.

IV. Practical Q&A: you must have encountered these situations

Q：Why do I still get blocked even if I use a proxy IP?
A: 80% is that the session is not handled properly! For example, the login status follows the IP, remember to clear the cookies every time you change the IP.

Q: What should I do if my proxy IP responds slowly?
A: First check if you are using a shared proxy, it is recommended to change to ipipgo's exclusive line. If it is an overseas resource, choose theirGeographically Customized Agentsmore effective

Q: What if I need to handle thousands of tasks at the same time?
A: on the asynchronous request ah! Use aiohttp with proxy pool, remember to control the concurrency. ipipgo's Enterprise Edition package supports 10,000 concurrency, but also with automatic load balancing!

V. Upgrade Play: Intelligent Agent Scheduling System

To the advanced players to share a masterpiece - dynamic intelligent scheduling. This program can automatically switch agents according to the response state of the target site, equivalent to the crawler installed an autopilot system.

from smart_proxy import IPManager   假设这是ipipgo的SDK

ip_manager = IPManager(api_key="你的ipipgo密钥")

def smart_request(url):
    while True:
        proxy = ip_manager.get_best_proxy()
        try:
            resp = requests.get(url, proxies=proxy)
            if resp.status_code == 200:
                return resp
            else:
                ip_manager.report_error(proxy)
        except:
            ip_manager.report_error(proxy)

 自动选择最低的节点
print(smart_request("https://需要抓取的网站"))

This solution is particularly suitable for large-scale crawler projects that need to run for a long time. ipipgo's API provides direct access to a list of real-time available proxies, and can also automatically troubleshoot failed nodes.

Sixth, say something heartfelt

Do crawler this line for more than five years, the biggest lesson is not to save money on the proxy IP. In the early years of using free proxies were pitched data leakage, but also encountered a proxy service provider suddenly run away, resulting in the collapse of the project. Later, I switched toipipgoThis regular service providers, not only the stability up, there are problems with technical customer service support at any time.

Finally, to remind novice friends: network capture to comply with the website robots agreement, control the frequency of capture. After all, we are just "borrowing data", do not get the other server down. Use a good proxy IP this tool, in order to stand firm in this era of data is king.