import-zig 0.15.3

Compile and import Zig functions at runtime without building a package

import-zig

pip install import-zig

import_zig provides the simplest possible interface for compiling and importing Zig code into Python, to enable easy experimentation and prototyping.

Additionally, the compile_to function outputs a compiled Python extension module for the target interpreter, which can be integrated into a larger Python package. Here is a setup.py of a Python package using compile_to in this way.

One fun thing about creating Python extensions with Zig is that you don't need to install or set up any compiler toolchain to use or build a module. The entire Zig compiler is a simple dependency on the ziglang Python package, which is the only dependency of import-zig.

Requirements

• Python 3.10 or newer.
• The package installs and invokes ziglang==0.15.1.
• Python development headers must be available so Zig can compile against the Python C API. On Linux this usually means installing python3-dev or python3-devel.

Quick start

from import_zig import import_zig

mod = import_zig(source_code="""
    pub fn Q_rsqrt(number: f32) f32 {
        const threehalfs: f32 = 1.5;
        const x2 = number * 0.5;
        var y = number;
        var i: i32 = @bitCast(y);
        i = 0x5f3759df - (i >> 1);
        y = @bitCast(i);
        y = y * (threehalfs - (x2 * y * y));

        return y;
    }
""")

print(f"1 / sqrt(1.234) = {mod.Q_rsqrt(1.234)}")

Choosing an input mode

Exactly one of source_code, file, or directory must be passed to import_zig() or compile_to().

• source_code: compile an inline Zig source string.
• file: compile a single .zig file.
• directory: compile a multi-file Zig project. This argument is a mapping with:
  • path: directory containing your Zig sources.
  • root_source_file: entry-point Zig file inside that directory.

Example using a directory:

from import_zig import import_zig

module = import_zig(
    directory={
        "path": "multiple_files",
        "root_source_file": "import_fns.zig",
    },
)

Development workflow with prepare

prepare() writes the Zig build scaffolding into an existing directory so you can work on a Zig project with editor support and compile it later with compile_prepared().

import import_zig

import_zig.prepare(
    "/path/to/project_folder",
    "module_name",
    "root_source_file.zig",
)

This generates the following files alongside your own Zig source tree:

project_folder
├── root_source_file.zig
├── build.zig
├── build.zig.zon
└── zig_ext
    ├── c.h
    ├── generated.zig
    ├── .gitignore
    ├── py_utils.zig
    └── zig_ext.zig

root_source_file.zig is your entry point and is never overwritten by prepare(). build.zig, build.zig.zon, and zig_ext/ are regenerated to match the current Python environment. On non-Windows platforms they are symlinked by default; on Windows, or when force_copy=True, they are copied instead.

This setup enables ZLS support for @import("c") and @import("py") inside your Zig sources.

Compiling to a reusable extension

Use compile_to() when you want a compiled extension file in a target directory instead of importing it immediately:

from import_zig import compile_to

compile_to(
    target_dir=".",
    module_name="my_module",
    file="single_file.zig",
)

The produced binary is platform-specific and will use Python's extension suffix for the current interpreter.

Use compile_prepared(target_dir, cwd) after a prepare() workflow. cwd must point at the prepared Zig project directory.

Build options and dependencies

The optimize argument is accepted by import_zig(), compile_to(), and compile_prepared(). Supported values are:

• Optimize.Debug
• Optimize.ReleaseSafe
• Optimize.ReleaseFast
• Optimize.ReleaseSmall

imports can be passed to prepare(), import_zig(), or compile_to() to populate build.zig.zon dependencies for Zig packages. Each dependency entry is written directly into the generated .dependencies section. If an import spec contains a path entry, it is rewritten relative to the prepared build directory.

Type mapping and Python interop

The conversion rules live in zig_ext/py_utils.zig and are applied based on the parameter and return types of exported pub fn functions. Nested conversions are handled recursively.

Conversion from Python	Zig datatype	Conversion to Python
int	integer (any size / sign)	int
float	float (any size)	float
bool(value) semantics	bool	bool
sequence	array	list
sequence	non-u8 slice	list
str	[]const u8	str
dict or sequence	struct	struct-like Python object, or tuple for Zig tuple structs
None	optional	null becomes None
not applicable	void	None

Additional interop behavior:

• If a function accepts std.mem.Allocator, an arena allocator is provided for the duration of the call. This lets the Zig code allocate return data such as string slices whose contents are converted to a Python string before the arena is deinitialized.
• Raw Python objects can be handled directly with *c.PyObject after importing c or py.
• Zig errors are forwarded to Python exceptions. Returning error.SomeName becomes a Python exception, and py_utils.zig also exposes helpers for raising Python exceptions explicitly.

Python C API helpers

Inside compiled Zig code you can use:

const c = @import("c");
const pyu = @import("py");
const py = pyu.py;

This gives access to the Python C API and the helper utilities bundled in py_utils.zig, including conversion helpers, exception helpers, and support used by the Arrow example in examples/arrow_example.zig.

Examples

See examples/basic_usage.ipynb for the main API surface, examples/prepare_development.ipynb for the prepared-project workflow, and examples/arrow_example.zig plus examples/arrow_example.ipynb for lower-level Python C API interop.