Python Web Crawling Tutorial: From Beginner to Proficient

First, why is your crawler always pulled by the site?

Crawler friends understand that the biggest headache is just run two minutes, the IP is sealed to death. The site is not a fool, see the same IP crazy request, directly shut down the dog. At this time you need to find a substitute to help you carry the mine -proxy IPJust an excellent choice.

As a chestnut, you want to catch the price of a certain e-commerce platform. With their own broadband connected to the request 50 times, the server immediately give you a seal. If you change the IP address for each request, the site can't tell if it's a real person or a program.distributed stealthThe

import requests
from itertools import cycle

 API interface provided by ipipgo (remember to replace it with your own account)
proxy_pool = [
    'http://username:password@gateway.ipipgo.com:8001',
    'http://username:password@gateway.ipipgo.com:8002'
]

proxy_cycle = cycle(proxy_pool)

for page in range(1, 101):
    try: proxy = next(proxy_cycle).
        proxy = next(proxy_cycle)
        response = requests.get(
            f'https://example.com/products?page={page}',
            proxies={'http': proxy}, timeout=10
            timeout=10
        )
        print(f'Page {page} captured successfully')
    except.
        print('This IP hangs, switch to the next one now')

Second, proxy IP in the end how to choose reliable

The market is full of proxy service providers, but there are also a lot of pitfalls. Some free proxies look beautiful, but in reality they are slower than a snail, and some of them are simply fake IP addresses.Tips for avoiding pitfalls::

Here's the kicker.Dynamic Residential AgentsThis kind of IP is exactly the same as the IP of a normal user, so the website can't detect any abnormality at all. ipipgo such service providers also provide automatic change interval settings, and it is recommended to change the IP once every 5-10 requests.

Third, hand to teach you to match the agent

Here take Python's requests library as an example, in fact, the principles are similar. The key is to handle theException Retry MechanismDon't let the whole program crash just because one IP fails.

import random
import time

def smart_crawler(url): max_retry = 3
    max_retry = 3
    for _ in range(max_retry):: _ in range(max_retry).
        try.
             Randomly choose a proxy
            proxy = random.choice(ipipgo_proxies)

            response = requests.get(
                response = requests.get(
                proxies={'http': proxy},
                headers=random_headers, remember to disguise the request headers
                timeout=8
            )

            if response.status_code == 200.
                return response.text

        except Exception as e: print(f "Error: {str(e)}")
            print(f "Error: {str(e)}")
            time.sleep(2) Fail and try again later.

    return None

Watch this.randomized sleepThe tip, don't always request at the whole time, it is easy for the anti-crawl system to catch the pattern. It is recommended to stop randomly between 2-5 seconds to simulate a real person's operation.

Fourth, the actual combat: e-commerce price monitoring case

Let's say we want to monitor the price changes of 10 items on a platform, captured 3 times a day. Directly on the dry code:

import schedule
from concurrent.futures import ThreadPoolExecutor

product_ids = ['123', '456', '789'] Example product IDs

def fetch_price(product_id):
    proxy = ipipgo.get_proxy() call ipipgo's API to get a new IP
    try.
        resp = requests.get(
            f'https://shop.com/product/{product_id}',
            proxies={'http': proxy},
            headers={'User-Agent': 'Mozilla/5.0'}
        )
         Here's the code to parse the price
        save_to_database(product_id, price)
    except.
        ipipgo.report_failure(proxy) flagging failed IPs

def job().
    with ThreadPoolExecutor(max_workers=5) as executor.
        executor.map(fetch_price, product_ids)

 Execute at 8:00, 14:00 and 20:00 every day
schedule.every().day.at("08:00").do(job)
schedule.every().day.at("14:00").do(job)
schedule.every().day.at("20:00").do(job)

while True: schedule.run_pending()
    schedule.run_pending()
    time.sleep(1)

There are three major highlights of this program:Multi-threaded acceleration,Automatic IP change,Abnormal IP Reporting. The API with ipipgo also automatically recovers invalid proxies to ensure that collection tasks are not interrupted.

V. Frequently Asked Questions QA

Q: What should I do if the proxy IP suddenly doesn't work?
A: Switch to a new IP immediately and contact your service provider. Like ipipgo has 24 hours technical support, the response time is twice as fast as the counterparts

Q: Which one to choose between HTTP and SOCKS5 protocols?
A: HTTP is enough for ordinary web pages, and SOCKS5 is needed to transmit encrypted data. ipipgo supports both protocols, and the background can be switched at any time.

Q: Is there a big difference between free proxies and paid proxies?
A: The difference between heaven and earth! The average survival time of free agents is less than 1 hour, paid agents like ipipgo's IP can be used for 3-7 days. Don't save money on important projects!

Q: Why do you recommend ipipgo?
A: Three hardcore reasons: 1. Exclusive IP does not queue 2. 30 provinces in the country IP optional 3. traffic is not capped. I've used it and I know that it saves more than the self-built proxy pool.

Sixth, the ultimate anti-sealing method of mind

Lastly, I'd like to pass on acombination::

1. Proxy IP + random request header double insurance
2. Important tasks to open ipipgo'sIP Rotation Model
3. Control the frequency of visits, don't bring down the web server
4. Clean Cookies Regularly, Don't Leave Small Tails

Remember to do the crawler topromote military ethicsDon't catch a site in a dead end. Comply with the robots agreement, the delay settings can not be less. Use the right tools plus the right way, collect data to be able to flow.