artFi/app/models.py

# Database Models
from . import db # that SQLAlchemy Object in __init__.py
from flask_login import UserMixin
from sqlalchemy.sql import func

class User(db.Model, UserMixin): # User Database
   id = db.Column(db.Integer, primary_key=True)
   email = db.Column(db.String(150), unique=True)
   password = db.Column(db.String(150))
   username = db.Column(db.String(150))
   profile_image = db.Column(db.String(150))

class Transaction(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    filehash = db.Column(db.String(64)) # sha256 hash
    datetime = db.Column(db.DateTime(timezone=True), default=func.now())
    source_id = db.Column(db.Integer)
    destination_id = db.Column(db.Integer)
    price = db.Column(db.Float)
    txhash = db.Column(db.String(64))

class Hashchain(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    blockhash = db.Column(db.String(64))