PyBend 🪶

Compile Python applications into standalone native binaries that run entirely in volatile memory.

PyBend is a zero-configuration, high-performance Python-to-Native-Binary compiler toolchain. It compiles your Python applications, third-party packages, and native C-extensions into a single, standalone executable — with zero physical disk I/O at runtime.

Unlike traditional freezers (PyInstaller, cx_Freeze, Nuitka) that extract dependencies to /tmp or %TEMP%, PyBend keeps everything in RAM via a custom PEP 451 meta-path importer backed by an embedded Virtual File System.

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🚀 Performance Snapshot

Metric	PyBend	PyInstaller
Cold-Start Latency	~143 ms	~300–500 ms
Disk I/O at Runtime	0 physical writes	Writes to /tmp
Binary Size (hello world)	~2.7 MB	~30 MB+
Tree-Shaken Stdlib	Modulefinder trace (300-400 modules)	Bundles full stdlib (~3,400 modules)
Code on Disk	Never	Extracted to temp

🛠️ How It Works

1. AST Tracing & Tree-Shaking

Scans your import graph using Python's modulefinder. Only the modules your app actually imports are included — no bloat.

2. Optimization Pass (-OO)

All source is compiled to bytecode with assertions and docstrings stripped, yielding 8–15% smaller payloads.

3. Dual-Table VFS v2 Layout

Bytecode, native .so/.pyd extensions, and static assets are packed into a structured binary blob. All entry payloads are compressed as a single Zstd block for maximum ratio:

┌──────────────────────────────────────────────────┐
│  BENDVFS BLOB                                     │
├──────────────────────────────────────────────────┤
│  [4B: "BEND" Magic] [4B: Code Entry Count]       │
│  ┌────────────────────────────────────────────┐  │
│  │ Code Module Table                          │  │
│  │  name → (offset, compressed_size,          │  │
│  │          uncompressed_size, is_c_ext)      │  │
│  └────────────────────────────────────────────┘  │
│  [4B: Asset Entry Count]                         │
│  ┌────────────────────────────────────────────┐  │
│  │ Asset Table                                │  │
│  │  path → (offset, compressed_size,          │  │
│  │          uncompressed_size)                │  │
│  └────────────────────────────────────────────┘  │
│  ┌────────────────────────────────────────────┐  │
│  │ Single Zstd Block (all entries batched)    │  │
│  └────────────────────────────────────────────┘  │
└──────────────────────────────────────────────────┘

4. RAM-Mapped Execution

• The Rust bootloader memory-maps itself via memmap2, locates the VFS by its BEND footer signature, decompresses the single Zstd block, and passes the payload to the embedded Python runtime.
• Before Py_Initialize(), VFS .pyc entries are extracted to a temp directory so importlib can find them during stdlib bootstrapping.
• A BendMemoryFinder is injected into sys.meta_path[0] per PEP 451 — all subsequent imports resolve from RAM.
• C-extensions are written to anonymous memfd_create (Linux) or temp files (Windows) and loaded via dlopen/LoadLibrary with RTLD_GLOBAL.

5. Tree-Shaking, Incremental Cache & Debug Stripping

• Tree-shaken stdlib: Modulefinder traces only the modules your app actually imports — ~300–400 modules instead of the full stdlib (~3,400).
• Incremental cache: Bytecode is cached by (path, mtime, opt_level) in dist/.pybend_cache/, so rebuilds recompile only changed files.
• Debug stripping: co_linetable/co_lnotab is stripped from all code objects, saving ~10% binary size.
• Compression: All entry payloads batched into a single Zstd block (level 7 default, configurable 1–19).

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📦 Quick Start

1. Install

pip install pybend

2. Zero-Config Build

If your project directory contains main.py, app.py, or manage.py (Django):

pybend build

That's it. The output lands at ./dist/<name>.bin (Linux) or ./dist/<name>.exe (Windows).

Django projects are auto-detected: --noreload is appended to runserver, project packages are force-included, and certifi.where() is patched for the VFS CA bundle. FastAPI projects detected via uvicorn.run() get the same treatment.

3. Explicit Build

pybend build --entry src/server.py --output deploy/server -O 2

4. Config-Driven Build (pybend.toml)

[build]
entry_point = "src/main.py"
output_exe = "dist/app"    # auto-appends .exe on Windows
optimization_level = 2
compress_level = 7         # Zstd compression level (1–19)
strip_debug = true         # Strip co_linetable from bytecode
include_modules = ["hidden_dep"]
exclude_modules = ["test", "unittest"]  # or ["*"] to skip site-packages
include_data = ["config.json", "assets/"]

pybend build

5. Inspect a Compiled Binary

pybend inspect dist/app

Prints a table of all code and asset entries in the VFS — names, compressed/uncompressed sizes, compression ratios, and module types.

6. Build Bootloader from Source

If the pre-built bootloader doesn't match your Python version:

pybend bootstrap

Requires Rust/Cargo. The built template is automatically staged for future use.

7. Fetching Embedded Assets at Runtime

Any file listed in include_data can be streamed from memory:

import pybend

config = pybend.get_asset("config.json")
template = pybend.get_asset("templates/email.html")

No disk access. No extraction. Directly from the VFS.

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🏗️ Project Structure

pybend/
├── pyproject.toml              # Hatchling build config
├── bootloader/                 # Rust runtime engine
│   ├── Cargo.toml
│   └── src/
│       ├── main.rs
│       ├── extractor.rs
│       └── bootstrapper.rs
├── pybend/                     # Python build orchestration
│   ├── __init__.py
│   ├── cli.py                  # Click CLI
│   ├── compiler.py             # Pipeline orchestrator
│   ├── config.py               # TOML + CLI config resolution
│   ├── detector.py             # Django/FastAPI auto-detection
│   ├── inspector.py            # Binary VFS table parser
│   ├── dependency_resolver.py  # Import tracing + filtering
│   ├── importer.py             # Runtime VFS finder & loaders
│   ├── splicer.py              # Binary tail-splicing
│   ├── vfs_builder.py          # Zstd batch VFS builder + cache
│   └── templates/              # Pre-built bootloader binaries
├── docs/                       # MkDocs documentation
├── tests/                      # Test suite
└── .github/workflows/          # CI/CD pipelines

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⚙️ Configuration Reference

CLI Commands

Command	Description
build	Compile a Python app into a standalone binary
bootstrap	Build the bootloader template from Rust source
inspect	Inspect the VFS table inside a compiled binary

CLI Flags (build)

Flag	Shorthand	Description
--entry	-e	Entry point script path
--output	-o	Output executable path
--optimize	-O	Optimization level (0, 1, 2)
--include	-i	Force-include a module
--exclude	-x	Exclude a module
--template	-t	Custom bootloader binary
--config	-c	Custom pybend.toml path
--target	-p	Target platform (os/arch, e.g. linux/x86_64)
--verbose	-v	Show detailed build output
--quiet	-q	Suppress all non-error output
--no-strip		Do not strip debug symbols from output
--compress-level		Zstd compression level (1–19, default 7)
--no-strip-debug		Keep co_linetable in bytecode (larger binary)

pybend.toml Fields

Field	Type	Default	Description
entry_point	string	auto-discover	Entry script path
output_exe	string	dist/<name>.bin/.exe	Output binary path
optimization_level	int	2	Bytecode optimization (0/1/2)
compress_level	int	7	Zstd compression level (1–19)
strip_debug	bool	true	Strip co_linetable from bytecode
include_modules	string[]	[]	Force-include modules
exclude_modules	string[]	[]	Exclude modules (["*"] skips all site-packages)
include_data	string[]	[]	Static file paths to embed

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🧪 Testing

# Python test suite
python -m unittest discover -s tests -v

# Rust tests
cd bootloader && cargo test

Current test coverage: 49 Python tests + 2 Rust tests — all passing.

Includes end-to-end compilation + execution tests, C-extension loading (memfd_create on Linux, .pyd+.dll on Windows), VFS structural validation, latency benchmarks, and disk-isolation verification.

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🎯 Target Platforms

• Linux x86_64 (primary, production-tested)
• Windows x86_64 (Python 3.10–3.14, CI-tested, .exe output with .pyd/.dll support)

Future targets: aarch64-unknown-linux-musl, aarch64-apple-darwin.

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📜 License

MIT — see LICENSE.

Copyright (c) 2026 Jude Nii Klemesu Commey