OBSOLETE, see comment below ||| Connection to the Firestore emulator in python, since it wasn't at that time supported by the official SDK, see https://github.com/googleapis/google-cloud-python/issues/7500

firestore_emulator.py

import os
from unittest import mock

import grpc
from google.auth.credentials import Credentials
from google.cloud import firestore
from google.cloud.firestore_v1.gapic import firestore_client
from google.cloud.firestore_v1.gapic.transports import firestore_grpc_transport


def get_firestore_client() -> firestore.Client:
    """
    Return a firestore Client, connects to an emulator if FIREBASE_FIRESTORE_EMULATOR_ADDRESS is set

    eg, using https://firebase.google.com/docs/functions/local-emulator

    firebase emulators:start --only firestore
    :return:
    """

    emulator_address = os.environ.get("FIREBASE_FIRESTORE_EMULATOR_ADDRESS")

    if emulator_address:
        dummy_project = "foo"
        dummy_credentials = mock.MagicMock(spec=Credentials)

        db = firestore.Client(project=dummy_project, credentials=dummy_credentials)

        # hack - set the internal firestore api client to point at the emulator,
        # used by ref: google.cloud.firestore_v1.client.Client._firestore_api
        print(f"connecting to firestore emulator at {emulator_address}")
        channel = grpc.insecure_channel(emulator_address)
        transport = firestore_grpc_transport.FirestoreGrpcTransport(channel=channel)
        db._firestore_api_internal = firestore_client.FirestoreClient(transport=transport)
    else:
        db = firestore.Client()

    return db

Thank you @therefromhere! This is very useful for me 🙂

I'm waiting for the Firebase Authentication <-> python admin sdk integration. For those who are interested:
firebase/firebase-admin-python#531