Python Web Scraping Essentials: GET/POST, Proxies, Cookies, and Multithreading

Python is one of the most popular languages for rapid web development, crawling, and automation.

1. Basic Page Fetching

Use the GET method to retrieve web pages and the POST method to submit data.

2. Using Proxy IPs

When a server blocks your IP, configure a proxy using urllib2.ProxyHandler to route requests through another address.

3. Cookies Handling

Websites store session data in cookies. Python’s cookielib module provides a CookieJar object that works with urllib2 to manage cookies automatically.

Manual cookie addition can also be performed as shown.

4. Spoofing as a Browser

Some sites reject non‑browser requests, returning HTTP 403. Set appropriate request headers such as User-Agent and Content-Type to mimic a real browser.

5. Captcha Handling

Simple captchas can be recognized automatically; more complex ones (e.g., 12306) often require third‑party solving services.

6. Gzip Compression

Servers can send compressed responses to reduce bandwidth. Add an Accept‑Encoding: gzip header to request compressed data, then decompress it after receiving.

7. Multithreaded Concurrent Fetching

Single‑threaded crawling can be slow. A simple thread‑pool template demonstrates concurrent fetching, which, despite Python’s GIL, can improve I/O‑bound crawling performance.