db_setup.py

import sqlite3
from sqlite3 import Error

def create_connection():
    conn = None
    try:
        conn = sqlite3.connect('mydb.db') # create a persistent database
        return conn
    except Error as e:
        print(e)

def create_tables():
    conn = create_connection()
    try:
        conn.execute('''CREATE TABLE IF NOT EXISTS interest_rates
                          (asset text, interest_rate real, timestamp datetime default current_timestamp)''')
        conn.execute('''CREATE TABLE IF NOT EXISTS users
                         (_id text primary key, username text, password text)''')
        conn.execute('''CREATE TABLE IF NOT EXISTS user_assets
                     (user_id text, asset text, balance integer, timestamp datetime default current_timestamp,
                      FOREIGN KEY(user_id) REFERENCES users(_id))''')
        conn.execute('''CREATE TABLE IF NOT EXISTS borrowed_assets
                     (user_id text, asset text, amount integer, timestamp datetime default current_timestamp,
                      FOREIGN KEY(user_id) REFERENCES users(_id))''')
        conn.execute('''CREATE TABLE IF NOT EXISTS liquidations
                    (user_id text, asset text, amount integer, date datetime default current_timestamp)''')
        conn.commit()
    except Error as e:
        print(e)
    finally:
        if conn:
            conn.close()