Multiple databases in Flask

run.py

from flask import Flask, render_template, redirect, request, url_for, jsonify
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import text


app = Flask(__name__)
app.config["DEBUG"] = False
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False

"""
My PostgreSQL 10 installation listens on 5434, while 9.6 listens on 5432.
On both installations, I set user postgres to use 'trust' authentication for localhost only.
Note that SQLALCHEMY_DATABASE_URI still has to be configured.
"""
app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://postgres@localhost:5434/test"
app.config["SQLALCHEMY_BINDS"] = {
	"db_pg10": "postgresql://postgres@localhost:5434/test",
	"db_pg9_6": "postgresql://postgres@localhost:5432/test"
}


db = SQLAlchemy()
db.init_app(app)

"""
This is where the magic lies.
Courtesy of: https://stackoverflow.com/a/41291770
"""
e_pg10 = db.get_engine(app, "db_pg10")
e_pg9_6 = db.get_engine(app, "db_pg9_6")


@app.route("/")
def root():
	resp =	{
		"data_from_pg10": "",
		"data_from_pg9_6": "",
		"error": ""
		}


	try:
		res_from_pg10 = e_pg10.execute(text("select version();")).fetchone()
		if res_from_pg10 is not None:
			resp["data_from_pg10"] = res_from_pg10[0]


		res_from_pg9_6 = e_pg9_6.execute(text("select version();")).fetchone()
		if res_from_pg9_6 is not None:
			resp["data_from_pg9_6"] = res_from_pg9_6[0]


		resp = jsonify(resp)
		resp.status_code = 200
	except Exception, e:
		resp["error"] = str(e)

		resp = jsonify(resp)
		resp.status_code = 500
	finally:
		db.session.close()

		return resp


if __name__ == "__main__":
	app.run()