Use Case: python/cpython - The Python Interpreter

Repository: https://github.com/python/cpython Stack: Python (+ C) Test Date: 2025-12-08 Loctree Version: 0.6.2-dev

Overview

Testing loctree on THE Python interpreter source - the reference implementation of Python.

Repository Scale

Metric	Value
Python Files	842 (stdlib)
Analysis Time	25.09 seconds
Throughput	33 files/sec

Findings

Dead Code Detection

High Confidence: 278 candidates (v0.6.1)
False Positive Rate: 100% without library mode
With --library-mode: Auto-detects stdlib, excludes __all__ exports

Why Library Mode Matters (v0.6.x)

Without library mode, all flagged exports are public API for external use:

calendar.APRIL - Public API constant
csv.DictWriter - Core utility class
ftplib.all_errors - Used by urllib, socket, asyncio
typing.override - Used across stdlib

v0.6.x improvements:

Auto-detects Lib/ directory as stdlib
Respects __all__ declarations in modules
Use --library-mode for proper stdlib analysis

Additional Findings

Dead Parrots: 172 classes/functions
Circular Dependencies: 2 lazy cycles (both safe)

Known Issue

Unicode Bug Found: Devanagari numerals (like ६) in test files caused panic at py.rs:224:32. Test directory excluded to complete scan.

Status: Fixed in subsequent patch using bytes_match_keyword.

Commands Used

cd cpython
loct                              # Create snapshot
loct dead --confidence high       # Dead code analysis
loct cycles                       # Circular dependencies

Verdict

LIBRARY MODE REQUIRED - Use --library-mode for proper stdlib analysis (v0.6.x).

Key Insights

Performance: Fast and stable (33 files/sec)
Accuracy: Requires library mode for public API analysis
v0.6.x: Auto-detection of stdlib, __all__ tracking implemented

Recommendations

For Python stdlib/library analysis:

Use --library-mode flag for automatic __all__ exclusion
Auto-detects Lib/ directory as Python stdlib
pyproject.toml parsing for public API hints
Focus on internal modules (_internal/, _impl/) for application code