depyo 0.2.0

Python bytecode decompiler for Python 1.0 through 3.15 (Python port of depyo.js)

depyo

Python bytecode decompiler for Python 1.0 through 3.15.

This is the Python port of depyo.js. The JavaScript version is the canonical implementation and is ~4–5× faster; this port exists so you can hack on decompilation logic in Python without a Node runtime.

Status

• Fixture parity with JS baseline: 1183 / 1216 byte-identical (97.3%) across the full fixture suite (Python 1.0–3.15).
• Port-only bugs: 0. The 33 remaining diverging fixtures fail identically on the JS side — they're shared bug-for-bug parity, not port defects.
• Bytecode coverage: Python 1.0 through 3.15.

Install

pip install depyo

Or from source:

pip install -e .

Usage

depyo my_script.pyc
# → writes my_script.py next to the input

All JS CLI flags are supported (--asm, --debug, --raw, --dump, --stats, --strict, --py-version, --basedir, --out, --skip-source-gen, --skip-path, --marshal, --marshal-scan, --file-ext). Run depyo --help for the full list.

Speed

Measured across 1216 .pyc fixtures, 10 passes each:

Runtime	ms/file	pyc/s	Relative
Node.js (V8) — depyo.js	0.47	2143	1.0×
CPython 3.12	2.48	402	5.3× slower
PyPy 3.10	3.87	259	8.3× slower

This port is ~4–5× slower than the JS original. Honest disclosure: if you need throughput, use the JS version. If you want to read and modify decompilation logic in idiomatic Python, use this one.

PyPy does not help — it's actually 35% slower than CPython on this workload. The fixtures are short-lived (fresh PycReader/PycDecompiler per file), so the JIT never warms up; hot paths are also heavy on hasattr/getattr/isinstance against polymorphic shapes, which PyPy doesn't specialize well.

Scope

Decompiles .pyc / .pyo from Python 1.0 through 3.15, including:

• All control flow (if/elif/else, while, for, try/except/finally, with, match/case)
• Comprehensions (list, set, dict, generator, async)
• Functions, classes, decorators, async def, coroutines
• PEP 695/696 generic type syntax (3.12+)
• PEP 750 template strings (3.14+)

License

MIT — see LICENSE.

Copyright (c) 2011–2026 Sergey Kuznetsov.