Implementing Python API service

First create a main.py file in the src/pi_api directory and add the following code to it:

import math
from typing import Annotated

from fastapi import FastAPI, HTTPException, Query
from pydantic import BaseModel
from rust_pidigits import chudnovsky_pi

app = FastAPI()


MAX_DIGITS = math.ceil((2**32 - 1) / 4)


@app.get("/pidigits/")
async def pidigits(
    digits: Annotated[int, Query(ge=0, lt=MAX_DIGITS)],
    limit: Annotated[int | None, Query(gt=0, lt=MAX_DIGITS)] = None,
) -> str:
    try:
        if limit is not None:
            return chudnovsky_pi(digits)[: limit + 2]
        return chudnovsky_pi(digits)[: digits + 2]
    except (ValueError, OverflowError) as ex:
        raise HTTPException(
            status_code=400,
            detail=str(ex),
        )


class HealthResponse(BaseModel):
    status: str


@app.get("/healthz")
async def healthz() -> HealthResponse:
    return HealthResponse(status="ok")

Here we are using FastAPI to create a simple API service. We have two endpoints: /pidigits/ and /healthz. The /pidigits/ endpoint takes two query parameters: digits and limit. The digits parameter is used to determine the number of pi digits to return. The limit parameter is used to limit the number of pi digits to return. The /healthz endpoint is used to check the health of the API service. The /healthz endpoint returns a simple JSON object with the status ok.

Because this is a very simple API, we have defined endpoints in the same file as the main function. In a real-world application, you would probably define the endpoints in a separate file.

Our rust extension can be imported with from pidigits_rust import chudnovsky_pi. pidigits-rust being the name of the Rust extension and chudnovsky_pi being the name of the function we want to import. You can read more about PyO3's module structure here.

Before we can run our API service, we need to install our Rust extension. We can install the wheel file directly with pip:

pip install rust-pidigits/target/wheels/pidigits-0.1.0-cp312-cp312-manylinux_2_34_x86_64.whl

or we can install the wheel file with Poetry:

poetry run pip install rust-pidigits/target/wheels/pidigits-0.1.0-cp312-cp312-manylinux_2_34_x86_64.whl

Now we are ready to run our API service! 🎉