Decompile Python bytecode (.pyc) files back to readable Python source code. Supports Python 2.7 to 3.8, runs entirely in browser without backend servers.
Features
- Smart Bytecode Decompilation: Automatically reverse engineer Python .pyc bytecode files back to readable source code with intelligent AST reconstruction and control flow analysis.
- Multi-Version Python Support: Compatible with Python 2.7 to 3.13+ versions, automatically detecting bytecode format and applying version-specific decompilation algorithms for accurate results.
- Detailed File Metadata: Extract and display comprehensive file information including Python version, magic number, compilation timestamp, and bytecode structure for thorough analysis.
- Easy Export and Sharing: One-click copy decompiled source code to clipboard or download as .py file for immediate use in your projects and development workflow.
Usage Guide
- Step 1: Click 'Load File' to select a .pyc file from your computer.
- Step 2: The tool will automatically decompile the bytecode and display the Python source code.
- Step 3: Copy or download the decompiled Python code for your analysis.
Technical Details
Python Decompilation Process and Bytecode Reconstruction
Decompiling PYC files to Python source code involves reverse engineering bytecode back to high-level Python syntax. The process includes: PYC file parsing (extracting magic number, timestamp, code objects), bytecode instruction decoding (using dis module to understand operation sequence), control flow graph reconstruction (identifying branches, loops, exception handling), and Abstract Syntax Tree (AST) generation (building syntactic structure rep
Decompilation Algorithms and AST Reconstruction
Modern decompilers use sophisticated algorithms: control flow analysis (building Control Flow Graph from bytecode jumps, identifying structured control constructs from goto-like jumps), dataflow analysis (tracking variable definitions and uses, type inference from operations), and pattern-based reconstruction (matching bytecode instruction sequences to Python syntax patterns). AST generation involves: creating node hierarchy (Module → FunctionDef
Legal Considerations and Practical Applications
PYC decompilation serves legitimate purposes but involves legal and ethical considerations. Valid use cases include: legacy code recovery (retrieving source when originals lost, maintaining unmaintained projects), security analysis (auditing closed-source Python applications for vulnerabilities, malware reverse engineering), educational purposes (studying Python internals, learning compiler/decompiler techniques), and
Frequently Asked Questions
- What is a .pyc file and how is it created?
- .pyc files are Python bytecode files created when Python imports a module. Python compiles .py source files to bytecode (.pyc) for faster execution on subsequent runs. The .pyc file contains: magic number (identifying Python version), timestamp or hash (for cache validation), and marshalled code objects (bytecode instructions). These files are stored in __pycache__ directories and allow Python to skip compilation step on re-import, improving startup time.
- Can decompiled code be identical to the original source?
- No, decompiled code cannot be 100% identical to the original source. During compilation, Python loses: comments and docstrings (unless in code objects), original variable names in some contexts, formatting and whitespace, and certain high-level constructs that compile to similar bytecode. However, decompilers can reconstruct functionally equivalent code that performs the same operations. The accuracy depends on Python version, optimization level, and code complexity.
- Which Python versions are supported for decompilation?
- Most modern decompilers support Python versions from 2.7 to 3.11+. Each Python version uses different bytecode formats with unique magic numbers and opcodes. The tool attempts to detect the Python version from the .pyc file header and use appropriate decompilation algorithms. However, very new Python versions (3.12+) or very old versions (pre-2.6) may have limited support. For best results, ensure the decompiler version matches or supports your target Python version.
- Is it legal to decompile .pyc files?
- Legality depends on context and jurisdiction. Legal uses include: recovering your own lost source code, security analysis of software you own or have permission to audit, educational research into Python internals, and debugging applications where source is unavailable. However, decompiling commercial software, proprietary applications, or copyrighted code without permission may violate licensing agreements, intellectual property laws, or terms of service. Always respect software licenses and use decompilation only for legitimate, authorized purposes.
Related Documentation
- Python.org - Bytecode Internals - Official Python bytecode and compiler internals documentation
- PEP 552 - Deterministic pycs - Python Enhancement Proposal for .pyc file format
- uncompyle6 - Python Decompiler - Popular Python bytecode decompiler tool and library
- Python AST Module - Abstract Syntax Trees in Python documentation
- Python Code Objects - Understanding Python code object internals