wigners 0.3.0

Compute Wigner 3j and Clebsch-Gordan coefficients in pure Rust
Documentation 
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import os
import sys
import subprocess

from setuptools import setup, Extension
from setuptools.command.build_ext import build_ext
from wheel.bdist_wheel import bdist_wheel

ROOT = os.path.realpath(os.path.dirname(__file__))

if sys.version_info < (3, 6):
    sys.exit("Sorry, Python < 3.6 is not supported")

if "--rust-target" in sys.argv:
    index = sys.argv.index("--rust-target")
    RUST_TARGET = sys.argv[index + 1]

    # remove rust target from CLI args
    sys.argv.pop(index)
    sys.argv.pop(index)
else:
    RUST_TARGET = None


class universal_wheel(bdist_wheel):
    # When building the wheel, the `wheel` package assumes that if we have a
    # binary extension then we are linking to `libpython.so`; and thus the wheel
    # is only usable with a single python version. This is not the case for
    # here, and the wheel will be compatible with any Python >=3.6. This is
    # tracked in https://github.com/pypa/wheel/issues/185, but until then we
    # manually override the wheel tag.
    def get_tag(self):
        tag = bdist_wheel.get_tag(self)
        # tag[2:] contains the os/arch tags, we want to keep them
        return ("py3", "none") + tag[2:]


class cargo_ext(build_ext):
    """
    Build the native library using cargo
    """

    def run(self):
        cargo_build = ["cargo", "build", "--release"]
        target_dir = os.path.join(ROOT, "target")

        if RUST_TARGET is not None:
            cargo_build += ["--target", RUST_TARGET]
            target_dir = os.path.join(target_dir, RUST_TARGET)

        subprocess.run(cargo_build, cwd=ROOT, check=True)

        file_found = False
        for filename in ["libwigners.so", "libwigners.dylib", "wigners.dll"]:
            lib_path = os.path.join(target_dir, "release", filename)
            if os.path.exists(lib_path):
                file_found = True
                print(f"found native library at {lib_path}")
                self.copy_file(
                    lib_path, os.path.join(self.build_lib, "wigners", "_wigners.so")
                )

        if not file_found:
            raise Exception("failed to build native code")


# read version from Cargo.toml
with open("Cargo.toml") as fd:
    for line in fd:
        if line.startswith("version"):
            _, version = line.split(" = ")
            # remove quotes
            version = version[1:-2]
            # take the first version in the file, this should be the right one
            break

if __name__ == "__main__":
    setup(
        version=version,
        ext_modules=[
            # only declare the extension, it is built & copied as required in the
            # build_ext command
            Extension(name="wigners", sources=[]),
        ],
        cmdclass={
            "build_ext": cargo_ext,
            "bdist_wheel": universal_wheel,
        },
    )