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: 1236 / 1236 byte-identical (100%) across the full fixture suite (Python 1.0–3.15) as of v1.2.4. Direct stdout-vs-stdout comparison, not just snapshot match.
• Port-only bugs: 0. Both ports also raise on the same 10 fixtures (shared opcode-handler gaps — extractContextManager, Py2.7 WITH tuple-unpack — tracked, 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 1236 .pyc fixtures, 10 passes each:

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.