MonolithPy is a fork of CPython (currently based on Python 3.13) that produces fully statically linked Python interpreters. It is designed for creating portable, self-contained Python distributions.

• ☑ Static linking on all platforms (performance and lock down)
• ☑ Windows 7 support retained
• ☑ LTO (Link Time Optimization) for performance and smaller binaries
• ☑ Automatic source compilation for pip installs
• ☑ Embedded resources (SSL certificates, VFS)
• ☑ Package-wide symbol renaming for compatibility
• ☐ Support all major packages and provide upstream guidance

MonolithPy must be built from source. Deploying binaries is impractical because installing packages afterward requires recompiling the interpreter, so you need a working build environment regardless.

Prerequisites: Visual Studio with C++ build tools.

build.bat -x64

Options:

• -x64 - Build for 64-bit Windows (default)
• -x86 - Build for 32-bit Windows
• --pgo - Enable Profile-Guided Optimization
• -r - Rebuild from scratch

This produces a portable Python installation in the output folder (or output32 for 32-bit builds).

Prerequisites: build-essential, libc6-dev, gperf (on Debian/Ubuntu). The build script will attempt to install these automatically.

./build.sh [target_directory]

The script downloads and compiles all dependencies, then builds Python with LTO and PGO enabled. The default target is /opt/monolithpy<version>.

Example with custom target:

./build.sh ~/my-python

Prerequisites: Xcode command line tools.

./build.mac.sh [target_directory]

Options:

• --no-lto - Disable Link Time Optimization (faster build)

The script auto-detects architecture (arm64 or x86_64). The default target is ~/Library/MonolithPy<version>-<arch>.

Example:

./build.mac.sh ~/my-python

Cross-architecture build (Intel on Apple Silicon):

arch -x86_64 ./build.mac.sh

After building, the output folder contains:

• python / python.exe - The interpreter binary
• lib/ - Standard library and installed packages
• include/ - Python headers for building extensions
• dependency_libs/ - Compiled dependency libraries
• Embedded/ - Embedded resource data and object files

The output folder can be moved freely, even to other machines with the same OS/architecture. When you install packages via python -m pip, the interpreter will self-modify to statically link new native extensions.

Installing packages works normally, but with important differences:

./output/python -m pip install numpy

What happens:

1. pip downloads the source distribution (wheels are incompatible)
2. MonolithPy-specific build scripts may be fetched from the packages repo
3. The package is compiled with static linking
4. rebuildpython is invoked to relink the interpreter
5. The new interpreter includes the extension as a builtin module

Not all packages are supported. Packages requiring dynamic loading or incompatible build systems may fail. The goal is to support major packages and provide guidance for upstream fixes.

Unlike standard CPython which uses dynamic libraries (.so/.dll/.dylib), MonolithPy statically links all extension modules and dependencies directly into the interpreter binary. This produces a single, self-contained executable that can be deployed without external library dependencies.

When you install packages via pip, MonolithPy automatically relinks the interpreter to incorporate newly installed native extensions. The rebuildpython module scans for static libraries with Python init functions and regenerates the interpreter binary. This means:

• Installing a package may trigger a recompile of the interpreter
• The python executable will be replaced with a new version
• Link-time information is stored in link.json

MonolithPy includes an embedded virtual filesystem (VFS) for resources like SSL certificates. The mp_embed module provides file I/O interception to serve embedded files transparently. This allows the interpreter to function without external data files.

To avoid symbol conflicts when linking multiple static libraries, MonolithPy implements package-wide symbol analysis and renaming. This handles cases where different libraries (e.g., numpy, pybind11, cython) have conflicting symbol names.

MonolithPy builds all dependencies from source with static linking enabled. This includes:

• OpenSSL, SQLite, zlib, bzip2, xz/lzma
• libffi, mpdecimal, libb2
• ncurses, editline
• Tcl/Tk (with X11 dependencies on Linux)
• harfbuzz, freetype, fontconfig (for font rendering)

Copyright (c) 2021-2025 Nuitka Organization contributors. All rights reserved.

Copyright (c) 2001-2021 Python Software Foundation. All rights reserved.

Copyright (c) 2000 BeOpen.com. All rights reserved.

Copyright (c) 1995-2001 Corporation for National Research Initiatives. All rights reserved.

Copyright (c) 1991-1995 Stichting Mathematisch Centrum. All rights reserved.

See the file "LICENSE" for information on the history of this software, terms & conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.

This Python distribution contains no GNU General Public License (GPL) code, so it may be used in proprietary projects. There are interfaces to some GNU code but these are entirely optional.

All trademarks referenced herein are property of their respective holders.