How to use database models in Python Flask? - postgresql

Question

I'm trying to learn Flask and use postgresql with it. I'm following this tutorial https://realpython.com/flask-by-example-part-2-postgres-sqlalchemy-and-alembic/, but I keep getting error.
Cannot import name 'AorticStenosis' from partially initialized module 'models' (most likely due to a circular import)
I understand the problem, but I can't figure out how to fix it. So, I started playing around and try to use the steps by step tutorial on something that I'm working on, but I still get the same problem.
Here's my attempt:
Models.py
from app import db
class AorticStenosis(db.Model):
__tablename__ = 'wvu-model'
id = db.Column(db.Integer, primary_key=True)
ip_address = db.Column(db.String())
date_created = db.Column(db.DateTime, default=datetime.utcnow)
e_prime = db.Column(db.Float())
LVMi = db.Column(db.Float())
A = db.Column(db.Float())
LAVi = db.Column(db.Float())
E_e_prime = db.Column(db.Float())
EF = db.Column(db.Float())
E = db.Column(db.Float())
E_A = db.Column(db.Float())
TRV = db.Column(db.Float())
prediction = db.Column(db.String())
def __init__(self, ip_address, e_prime, LVMi, A, E_e_prime, EF, E, E_A, TRV, prediction):
print('initialized')
self.ip_address = ip_address
self.e_prime = e_prime
self.LVMi = LVMi
self.A = A
self.LAVi = LAVi
self.E_e_prime = E_e_prime
self.EF = EF
self.E = E
self.E_A = E_A
self.TRV = TRV
self.prediction = prediction
def __repr__(self):
return '<id {}>'.format(self.id)
app.py
import os
import ast
import bcrypt
from flask import Flask, redirect, render_template, request, session, url_for
import flask_login
from flask_sqlalchemy import SQLAlchemy
from bigml.deepnet import Deepnet
from bigml.api import BigML
import pickle as pkl
import sklearn
app = Flask(__name__)
if app.config['ENV'] == 'production':
app.config.from_object('as_config.ProductionConfig')
else:
app.config.from_object("config.DevelopmentConfig")
# app.config.from_pyfile('as_config.py')
# app.config.from_object(os.environ['APP_SETTINGS'])
# app.config.from_object('as_config.DevelopmentConfig')
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
from models import AorticStenosis
login_key = app.config['LOGIN_KEY']
api_key = app.config['API_KEY']
model = app.config['MODEL']
api = BigML(login_key, api_key)
deepnet = Deepnet(model, api=api)
scaler = pkl.load(open("scaler.pkl", "rb"))
#app.route("/", methods=["GET", "POST"])
def home():
prediction = None
if request.method == "POST":
form_data = [
float(request.form.get("e_prime")),
float(request.form.get("LVMi")),
float(request.form.get("A")),
float(request.form.get("LAVi")),
float(request.form.get("E_e_prime")),
float(request.form.get("EF")),
float(request.form.get("E")),
float(request.form.get("E_A")),
float(request.form.get("TRV"))
]
form_data = scaler.transform([form_data])[0]
print(form_data)
prediction = str(deepnet.predict({
"e_prime": form_data[0],
"LVMi": form_data[1],
"A": form_data[2],
"LAVi": form_data[3],
"E_e_prime": form_data[4],
"EF": form_data[5],
"E": form_data[6],
"E_A": form_data[7],
"TRV": form_data[8]
}, full=True))
prediction = ast.literal_eval(prediction)
print(prediction)
## get ip address from the user
ip_address = request.environ['REMOTE_ADDR']
print("ip_address: ", ip_address)
try:
aorticStenosis = AorticStenosis(
ip_address = ip_address,
e_prime = form_data[0],
LVMi = form_data[1],
A = form_data[2],
LAVi = form_data[3],
E_e_prime = form_data[4],
EF = form_data[5],
E = form_data[6],
E_A = form_data[7],
TRV = form_data[8]
)
db.session.add(aorticStenosis)
db.session.commit()
except Exception as e:
print(str(e))
if prediction["prediction"] == "1":
prediction["prediction"] = "Low Risk"
prediction["probability"] = round(
1 - prediction["probability"], 6)
elif prediction["prediction"] == "2":
prediction["prediction"] = "High Risk"
else:
prediction["prediction"] = "No prediction was made!"
return render_template("home.html",
prediction=prediction["prediction"],
probability=prediction["probability"])
else:
return render_template("home.html")
if __name__ == "__main__":
app.run(host="0.0.0.0", port="8000")

Answer 1

I made a new file database.py and defined db there.
database.py
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
def init_app(app):
db.init_app(app)
app.py
import database
...
database.init_app(app)
models.py
from database import db
...