How to Debug Issues with a Specific Site Extractor in you-get

Enable the --debug flag to trace execution from the CLI through src/you_get/util/log.py into the site-specific extractor located in src/you_get/extractors/<site>.py, then inspect the prepare() and extract() methods to identify regex misses, JSON parsing errors, or signature decryption failures.

When a download fails for a specific site in the you-get repository, systematic debugging requires understanding how the extraction pipeline routes requests from the command-line interface to the site-specific implementation. The codebase provides built-in instrumentation through the util/log.py module and supports interactive debugging via Python REPL, allowing you to isolate whether failures occur during initial page fetching, stream extraction, or signature deciphering.

Understanding the you-get Extraction Architecture

The extraction framework follows a layered architecture that moves from generic CLI handling to site-specific logic:

• CLI Entry Point: src/you_get/__main__.py parses arguments including --debug and delegates to main_dev.py
• Logging Utility: src/you_get/util/log.py provides the log.d() debug wrapper that respects the DEBUG flag set via CLI
• Network Layer: src/you_get/common.py contains get_content() (line 463) and post_content() helpers that wrap HTTP requests
• Base Extractors: src/you_get/extractor.py defines the Extractor and VideoExtractor base classes
• Site Implementations: src/you_get/extractors/<site>.py files (e.g., youtube.py, bilibili.py) implement prepare() and extract() methods

Step-by-Step Debugging Workflow

Enable Verbose Output with --debug

Start by running your command with the --debug flag to activate verbose logging throughout the stack:

you-get --debug "https://www.youtube.com/watch?v=dQw4w9WgXcQ"

This flag toggles logging.debug calls defined in src/you_get/common.py around lines 1612-1616, enabling timestamped output from the util/log.py logger.

Trace the Execution Flow

The logger in src/you_get/util/log.py provides a d() function that prints debug messages only when the debug level is enabled:

# src/you_get/util/log.py

def d(msg, *args, **kwargs):
    if logging.getLogger().isEnabledFor(logging.DEBUG):
        print('[DEBUG]', msg % args, **kwargs)

When --debug is active, you will see output from the site extractor's prepare() method, such as logging.debug('Extracting from the video page...') in src/you_get/extractors/youtube.py around lines 224-236.

Locate the Site-Specific Extractor

The URL-to-extractor mapping resides in src/you_get/extractors/__init__.py. This registry imports classes like YouTube from youtube.py and BiliBili from bilibili.py, then returns the appropriate class via match_extractor(url).

Identify your target site's module (e.g., src/you_get/extractors/youtube.py) and examine its implementation of the prepare() and extract() methods.

Inspect the prepare() Method

The prepare() method handles initial page fetching and initial data extraction. In src/you_get/extractors/youtube.py around line 224, this method:

1. Fetches the video page using get_content() with custom headers
2. Extracts the ytInitialPlayerResponse JSON via regex
3. Retrieves the player JavaScript URL for signature deciphering

Look for debug statements surrounding these operations to verify HTTP success and regex matches. If the regex fails to find ytInitialPlayerResponse, the extraction stops before reaching stream parsing.

Analyze the extract() Method

This method populates self.streams or self.dash_streams with downloadable URLs. Key debugging points include:

• Signature Decryption: Look for s_to_sig and dethrottle calls. YouTube frequently updates base.js, breaking these functions. Check the comment block around lines 78-119 in youtube.py for the current deciphering logic.
• Stream Validation: Verify each stream entry contains a usable URL. Missing signature data triggers warnings like log.wtf('No signatureCipher ...').

Verify Network Requests

If HTTP requests fail, examine src/you_get/common.py where get_content() and get_https() reside. These functions accept a debuglevel parameter that passes to conn.set_debuglevel():

# Temporarily modify the call in prepare()

self.js = get_content(self.html5player, debuglevel=1).replace('\n', ' ')

Setting debuglevel=1 prints raw request/response headers to stderr, revealing TLS errors, redirects, or 403 Forbidden responses.

Add Custom Debug Statements

When built-in logs are insufficient, insert temporary debug lines using the utility logger:

from you_get.util import log
log.d('Current VID: %s', self.vid)
log.d('Player URL: %s', self.html5player)

Re-run with --debug to see these values without modifying global logging configuration.

Test the Extractor in Isolation

Bypass the CLI wrapper to test logic directly in a Python REPL:

>>> from you_get.extractors.youtube import YouTube
>>> yt = YouTube('https://youtu.be/dQw4w9WgXcQ')
>>> yt.prepare()
>>> yt.extract()
>>> yt.streams  # Inspect the generated URL dictionary

This approach eliminates argument parsing overhead and allows immediate inspection of yt.streams, yt.title, and intermediate variables.

Common Failure Points and Solutions

When debugging specific extractors, three issues occur most frequently:

• Regex Pattern Misses: Sites update their HTML structure, breaking patterns used in match1() (defined in src/you_get/common.py). Update the regex to match new page layouts.
• Player Code Changes: YouTube's base.js updates invalidate the s_to_sig deciphering algorithm. Monitor the player script URL logged in debug mode and update the transformation logic accordingly.
• Missing JSON Fields: API responses may exclude expected keys. Add defensive try/except blocks around json.loads() calls and log the raw response for analysis.

Summary

• Enable --debug to activate the util/log.py logger and see execution flow through src/you_get/__main__.py.
• Locate the extractor in src/you_get/extractors/<site>.py using the registry in __init__.py.
• Inspect prepare() for HTTP failures in get_content() calls and regex extraction of JSON/player data.
• Check extract() for signature decryption errors in s_to_sig and proper population of self.streams.
• Use debuglevel=1 in get_content() calls to inspect raw HTTP headers when network issues occur.
• Test interactively via Python REPL by importing the extractor class directly to bypass CLI overhead.

Frequently Asked Questions

How do I enable debug mode in you-get?

Run any command with the --debug flag. This sets the logging level to DEBUG in src/you_get/common.py (lines 1612-1616) and activates verbose output from src/you_get/util/log.py, showing HTTP requests, regex matches, and stream extraction steps.

Where are the site-specific extractors located?

Site extractors reside in src/you_get/extractors/ as individual Python modules (e.g., youtube.py, bilibili.py). The registry in src/you_get/extractors/__init__.py maps URL patterns to these classes. Each module implements prepare() to fetch metadata and extract() to populate stream URLs.

What should I check if a YouTube video fails to download?

First, verify the prepare() method in src/you_get/extractors/youtube.py successfully retrieves the page and extracts ytInitialPlayerResponse. If that passes, check the s_to_sig function (lines 78-119) for signature decryption errors, as YouTube updates base.js frequently. Enable --debug to see which specific step fails.

How can I test an extractor without using the CLI?

Import the extractor class directly into a Python REPL or script. For example, from you_get.extractors.youtube import YouTube, instantiate with a URL, and call prepare() followed by extract(). This allows inspection of self.streams and intermediate variables without CLI argument parsing overhead.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}