mleue/spiegel

Remote (mirrored) python objects.

The word spiegel is German for mirror. This library enables you to quickly expose/mirror a python class instance via a http server.

Installation

• install from pypi via pip install spiegel

What it is

In order to function, spiegel needs both a server and a client. The server uses an instance of your class and exposes an API via http which 1:1 mirrors the methods and properties on the object. If any of those endpoints is called, the server simply calls the respective method on the object it keeps locally. The client is started with your class and an address to the server. It replaces all methods and properties on the class with http requests to the respective endpoint on the remote mirror object that is running as an http server.

The client looks and behaves just like if you had a local instance of the object in memory, but instead it generates all behavior by communicating with the mirrored object.

Example

• define a simple Calculator class in a file calculator.py

class Calculator:
    def __init__(self):
        self._last_result = None

    @property
    def last_result(self) -> float:
        return self._last_result

    def sum(self, a: float, b: float) -> float:
        self._last_result = a + b
        return self.last_result

Server

• now create a server as follows in a file calculator_server.py

from spiegel.server import create_server
from calculator import Calculator

app = create_server(Calculator())

• the server uses fastAPI under the hood, so you can start it locally in the following way from your cli to be available at http://localhost:5000

$ uvicorn calculator_server:app --port=5000

• due to being based on fastAPI, an OpenAPI schema is automatically created and can e.g. be retrieved in swagger format at {address}:{port}/docs (i.e. in this example at localhost:5000/docs

Client

• now create a client as follows in a file calculator_client.py

from spiegel.client import create_client
from calculator import Calculator

if __name__ == "__main__":
    calculator = create_client(Calculator, "http://localhost:5000")()
    print(calculator.sum(1, 2))
    print(calculator.last_result)
    print(calculator.sum(2, 3))
    print(calculator.last_result)

• execute in a separate cli window/tab and the script should print the following as expected

$ python calculator_client.py
3
3
5
5

• you should also see the appropriate endpoints on the server being called

And that's it. Obviously it only gets really interesting once you put the server somewhere other than your local machine.