zuv 0.1.0

Bundle any uv project into a single runnable .py file.

zuv

zuv packs your entire uv project into a single .py file so you can hand it to a friend, drop it on a server, or attach it to an email and it just runs. The recipient only needs uv installed — no Python install, no pip install -r, no virtualenv setup, no folder structure to preserve.

uv run my-app.py

One file. One command. Same behaviour on any machine.

Why

Shipping a Python project usually means a zip, a README about setting up a venv, a requirements.txt, and a prayer that the recipient has the right Python version. zuv collapses all of that into one .py file that:

• Carries the whole project inside it (your src/, pyproject.toml, uv.lock, configs, assets — everything you don't .gitignore).
• On first run, extracts itself into .zuv/<name>_<hash>/ next to the script, lets uv build a .venv inside that folder, then runs your entry point.
• On every later run, skips the extraction and just executes.
• Stays tiny (under ~10 KB even for a FastAPI app) because dependencies are installed at runtime by uv from PyPI, not embedded.

Install

uv tool install zuv

Project layout

Any standard uv project works. The most common shape:

my-project/
  pyproject.toml          # [project] dependencies = [...]
  src/
    main.py               # an executable script (with if __name__ == "__main__")

main.py at the project root also works.

Build

From inside the project:

zuv build
# -> ./dist/<project-name>.py

Or point at a project explicitly:

zuv build ./my-project -o ./dist/my-app.py -e src/main.py

zuv build writes a fresh single-file script to the output path (use --clean to wipe the output's parent directory first). The entry point is resolved in this order:

By default, zuv build pre-compiles every .py to a sourceless .pyc (including the entry — Python and uv run both execute .pyc directly) and ships only bytecode. This ties the build to the builder's Python minor version because of marshal-format coupling. Pass --no-compile to keep .py sources instead; the loader will compile them at first extract, and the bundle stays portable across compatible Python versions.

1. --entry/-e flag
2. [tool.zuv].entry in pyproject.toml
3. src/main.py if it exists, otherwise main.py

Run

uv run dist/my-app.py
# or, equivalently, via zuv:
zuv run dist/my-app.py -- --any --args --you --like

The shebang + PEP 723 header makes uv run the canonical entrypoint; zuv run is a thin wrapper for users who don't want to remember which tool to invoke. First run: uv extracts the bundle, creates dist/.zuv/<name>_<hash>/.venv, installs deps, runs your entry. Subsequent runs go straight to executing.

Offline bundles (--deps)

Ship your app to machines with no internet. zuv embeds the wheels for your locked dependencies so the recipient runs it without ever hitting PyPI.

default build              --deps build
+------------------+       +-----------------------+
|  app.py  ~10 KB  |       |  app.py  ~tens of MB  |
+------------------+       |  + embedded wheels    |
| needs internet   |       +-----------------------+
| to install deps  |       | runs fully offline    |
+------------------+       +-----------------------+

How to use it

Bare --deps bundles for your current OS only (the common case — you build on Windows, you ship to Windows):

zuv build --deps

To target other platforms, pass labels (comma-separated) or all:

zuv build --deps all                   # every platform listed below
zuv build --deps linux                 # just Linux x86_64
zuv build --deps windows,linux         # Windows + Linux x86_64
zuv build --deps macos-arm,linux-arm   # ARM only

Available platform labels

+-------------+----------------------+
| label       | target               |
+-------------+----------------------+
| windows     | Windows x86_64       |
| linux       | Linux x86_64         |
| linux-arm   | Linux aarch64        |
| macos       | macOS Intel          |
| macos-arm   | macOS Apple Silicon  |
+-------------+----------------------+

Bundle size guide

no --deps           ~10 KB    (recipient needs internet)
--deps (host only)  ~few MB   (one platform)
--deps all          ~tens MB  (five platforms)

Notes

• Wheels are tied to the Python minor version you build with. A bundle built on Python 3.14 won't install offline on Python 3.13.
• Sdist-only deps are skipped (--only-binary=:all:). Those packages still need the network at install time on platforms where no wheel exists.
• The build host needs uv and internet access — the build itself downloads the wheels.

Try the included examples

zuv build examples/bigtest -o dist/bigtest.py
uv run dist/bigtest.py

zuv build examples/fastapi -o dist/fastapi.py
uv run dist/fastapi.py

Sibling overrides

The bundle's entry script runs with the extracted project folder as its CWD, so anything you would normally find next to your code (config files, frontend bundles, .env files) still works the same way.

Inspect a built file

zuv inspect dist/my-app.py

Prints the entry, build hash, SHA-256, Python cache tag, PEP 723 metadata, and a summary of the embedded loader bytecode. The payload itself is elided so the output stays useful for LLMs and code review.

Clear caches

zuv clean              # walk cwd, remove every .zuv/ found
zuv clean dist/        # or scope to a directory
zuv clean dist/app.py  # or to a built file (its parent is used)

The runtime also honors $ZUV_CACHE_DIR (and $ZUV_MAX_EXTRACT_BYTES for the decompression-bomb cap, default 2 GiB). If the script's directory isn't writable (system bin, read-only mount), the loader automatically falls back to $XDG_CACHE_HOME/zuv, %LOCALAPPDATA%\zuv, or ~/.cache/zuv.

A small caveat

Don't name your project the same as one of its dependencies. For example, a project named fastapi that depends on fastapi will confuse uv during install. Rename it to fastapi-example (or similar) and you're fine.

How it works

The output .py has five parts:

1. A #!/usr/bin/env -S uv run --script shebang and a PEP 723 metadata block declaring requires-python (no deps — uv reads those from the embedded pyproject.toml after extraction).
2. Metadata globals: _ZUV_ENTRY, _ZUV_BUILD_ID, _ZUV_SHA (sha256 of decoded payload), _ZUV_PY_TAG (build-time Python cache tag).
3. _ZUV_PAYLOAD — a deterministic tar.xz of your project tree, base85-encoded (uv's script runner requires UTF-8 source, which rules out raw-binary appends).
4. _ZUV_LOADER — the runtime loader, compile()d to bytecode then marshal+zlib+base85 (opaque to casual readers; verify with zuv inspect).
5. A 3-line stub that execs the loader, which then verifies the payload sha, extracts into .zuv/<stem>_<hash>/ with a .zuv-ready sentinel, and runs uv run --project <extracted> <entry>.

Dependencies aren't bundled inside the .py. uv installs them into the extracted project's local .venv on first run, so binary wheels work natively and the bundle stays small.

Layout

src/
  pyproject.toml
  zuv/
    cli.py                 # zuv CLI (build, inspect)
    builder.py             # tarball + base85 + compile loader + emit .py
    inspector.py           # zuv inspect
    _loader_template.py    # runtime loader embedded in every output
    constants.py
examples/
  bigtest/                 # rich + pydantic smoke test
  fastapi/                 # FastAPI + uvicorn web app