Using Python and Wget for Web Scraping

Jan 9, 2024 ยท 4 min read

Wget is a powerful command-line utility for downloading content from the web. This article will explore two main methods for harnessing Wget functionality in Python scripts:

  1. Using the Wget module
  2. Calling the Wget command via subprocess

Both approaches have their own pros and cons which I'll cover in detail below. Overall, Wget is extremely useful for web scraping and automation tasks thanks to features like:

  • Recursively download entire websites
  • Resume broken downloads
  • Customize user agent strings
  • Speed throttling options
  • Flexible filtering by file type, regex patterns, etc.
  • Let's look at how we can leverage these capabilities by invoking Wget from Python.

    Prerequisites

    Before using Wget from Python, you will need:

  • Python 3.6+
  • Wget installed on your system (likely already available on Linux/macOS)
  • For Windows: install Git Bash for access to Unix style tools like Wget
  • Importing the Wget Module

    Python has a built-in Wget module that exposes several convenient functions:

    import wget
    
    url = '<http://example.com/file.pdf>'
    
    wget.download(url) # Download to local file
    

    Some of the useful options this unlocks include:

  • Out-of-box progress bar for long downloads
  • Custom local filenames for downloaded files
  • Password authentication for protected resources
  • This wraps Wget functionality into simple Python method calls. However, we lose fine-grained control over arguments and options compared to the command line interface. When more configurability is needed, invoking Wget directly often works better.

    Calling Wget via Subprocess

    Python's subprocess module allows executing external programs from scripts and fetching the response data. Here is a simple example:

    import subprocess
    
    subprocess.run(['wget', '<http://example.com/files.zip>'])
    # Downloads files.zip from example.com
    

    By passing a list argument, we can add any flags and options as additional elements:

    subprocess.run([
      'wget',
      '--limit-rate=100k',
      '--user-agent="Custom User Agent String"',
      '<https://example.com/page.html>'
    ])
    

    This provides complete access to the full capabilities of the Wget CLI. Some things that may require using subprocess over the Wget module include:

  • Mirroring full websites recursively
  • Setting bandwidth throttling
  • Adding HTTP headers like user-agent strings
  • Using authentication credentials for protected sites
  • The tradeoff is subprocess introduces more complexity. We need to parse outputs to check for errors, handle streaming for long downloads, etc.

    Wget Functionalities

    Wget is packed with tons of useful features for downloading web content. Here are some of the main functions it provides:

    Recursive Downloading

    Wget can mirror entire website structures with the -r flag:

    subprocess.run([
      'wget',
      '-r',
      '-N',
      '-np',
      '<https://example.com>'
    ])
    

    This crawls all linked pages recursively. Helpful options include:

  • N - Only re-downloads newer versions of files
  • np - Doesn't ascend to parent directories
  • Resuming Downloads

    If a download gets interrupted, use -c to continue:

    subprocess.run([
      'wget',
      '-c',
      '<https://example.com/large_file.zip>'
    ])
    

    This retains the bytes downloaded so far and adds the remaining portions.

    User Agents

    Spoof custom user agent strings with --user-agent:

    subprocess.run([
      'wget',
      '--user-agent="Custom Browser 1.0"',
      '<https://example.com>'
    ])
    

    Helps avoid blocks from servers limiting automation.

    Rate Limiting

    Throttle download speed with --limit-rate (bytes per second):

    subprocess.run([
      'wget',
      '--limit-rate=3000k',
      '<https://example.com/video_file.mp4>'
    ])
    

    Prevents using up too much bandwidth.

    There are many more - timestamping, headers, attributes etc. Refer to Wget docs for full list.

    By scripting the command line Wget, you can leverage any of these versatile options for custom web scraping jobs.

    Conclusion

    In summary, Python and Wget work extremely well together for web scraping tasks. The Wget module provides a simple API for basic downloads while subprocess grants full access to advanced configuration options. Combining these approaches unlocks the benefits of Wget in an easy to use Python interface.

    Some examples where using Wget from Python shines:

  • Building local mirrors of websites
  • Downloading media files like video/music at scale
  • Grabbing data dumps from REST API endpoints
  • Automating retrieval of frequently updated resources
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