Python Decompiler Online

For packaged Python modules, type stubs, dependencies and native libraries in a .whl, use the Python Wheel Viewer and WHL Extractor. It preserves package contents without installing them.

What is a PYC File?

PYC stands for Python Compiled. When Python imports a module, the interpreter compiles the source code (.py file) into bytecode and caches the result as a .pyc file. This cached bytecode allows subsequent imports to skip the compilation step, improving startup time.

In Python 3, .pyc files are stored in __pycache__ directories with filenames that include the Python version (e.g., module.cpython-39.pyc). In Python 2, .pyc files were placed alongside the .py source files.

PYC File Structure

A PYC file contains:

• Magic number — identifies the Python version that generated the bytecode (each Python version uses a different magic number)
• Timestamp / hash — used for cache invalidation (timestamp-based in Python < 3.7, hash-based option in 3.7+)
• Source size — the size of the original .py file (Python 3.2+)
• Code object — marshalled Python code object containing bytecode, constants, variable names, and metadata

PYZ Files: Two Formats, One Extension

A .pyz upload is one of two unrelated things, and this service decides which from the file's own bytes rather than its name.

• A PyInstaller PYZ archive begins with PYZ\0 and holds one zlib-compressed module per entry — nearly the whole program of a frozen application. It is usually what is left over after unpacking an EXE. Each module is written out as a .pyc whose header carries the Python version that froze the archive, then decompiled where that version is supported.
• A zipapp (PEP 441) is an ordinary ZIP with __main__.py at its root, sometimes preceded by a #! line so it runs like a script. It normally contains real .py source, which is preserved exactly as packaged rather than regenerated; anything compiled without a packaged counterpart is decompiled alongside it.

The result keeps recovered source under sources/, bytecode under pyc/ and anything else the archive carried under resources/, so nothing is lost even when a module cannot be decompiled. Extraction works for every Python version; source recovery is limited by the bytecode decompiler, and a version it cannot read is named in the notes instead of being turned into misleading source. Nothing in the archive is ever imported or executed — __main__.py is treated as an ordinary file.

PYC vs PYO Files

PYO (Python Optimized) files were created when running Python with the -O flag, which removed assert statements and __debug__ code. In Python 3.5 (PEP 488), PYO files were deprecated and replaced by PYC files with optimization level suffixes like .cpython-39.opt-1.pyc.

Both PYC and PYO files contain the same type of bytecode and can be decompiled using this tool. The optimization level does not affect decompilation — only the removed assertions and debug code will be missing from the output.

How Python Decompilation Works

Python bytecode retains significant information about the original source code — variable names, function signatures, docstrings, line numbers, and code structure are all preserved. This makes Python decompilation much more effective than decompiling native code.

The decompiler reads the marshalled code object from the PYC file, analyzes the bytecode instructions, reconstructs control flow (if/else, loops, try/except), and generates Python source code that produces identical bytecode when recompiled.

Common Uses for Python Decompilation

• Recovering lost source code — when you have .pyc files but the original .py source was deleted
• Understanding packaged applications — many Python apps (PyInstaller, cx_Freeze) distribute only compiled bytecode
• Security analysis — examining Python-based malware or suspicious scripts
• Learning — studying how Python bytecode relates to source code

Python Packaged as an Executable

For an Android app built with Kivy, BeeWare or Chaquopy, use the Python APK decompiler to recover bundled Python alongside the Android source and resources.

If the bytecode is inside a Windows EXE, Linux executable, or macOS app built with PyInstaller or py2exe, upload the whole file to the PyInstaller decompiler. It unwraps the executable first, preserves the recovered .pyc files, and then runs this Python bytecode decompiler on each module.

Frequently Asked Questions