Efficient URL Requests with urllib PoolManager

Feb 6, 2024 ยท 2 min read

Making HTTP requests in Python is very common, whether you are scraping web pages, accessing APIs, or downloading files. The standard library's urllib module provides all the functionality you need to make these requests. However, making multiple requests can start to get slow, especially if you are requesting the same domains over and over.

This is where urllib's PoolManager comes in handy. The PoolManager allows you to pool connections to each host, avoiding the overhead of re-opening connections repeatedly.

Why Use a PoolManager?

Here's a typical example of making multiple requests without a pool manager:

import urllib.request

for url in urls:
    with urllib.request.urlopen(url) as response:
        data = response.read()

This works, but opening a new connection for every URL can be inefficient. This is where PoolManager helps - by reusing connections to each host.

Creating a PoolManager

To create a PoolManager, simply import PoolManager and provide the maximum number of connections to save:

from urllib.request import PoolManager

pool = PoolManager(max_pools=10) 

This will maintain up to 10 idle connections per host, avoiding connection overhead.

Making Requests

To make requests, use the pool.request() method instead of urllib.request.urlopen():

response = pool.request("GET", url)
data = response.read()

The pool manager handles opening and reusing connections automatically behind the scenes!

Tips and Tricks

  • Set a reasonable max for your application based on expected concurrency
  • Call pool.clear() to close all idle connections if no longer needed
  • Still abide by crawling politeness by adding delays
  • Using a PoolManager is a simple way to boost performance of Python applications that make multiple URL requests. Give it a try next time you need efficient reuse of connections!

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