models file I created for the CS50 finance project

models.py

from cs50 import SQL
import sqlite3

class users_db:
    def __init__(self, conn):
        self.id = ''
        self.conn = conn
        self.c = conn.cursor()

    def register(self, username, hash):
        row = self.c.execute('INSERT INTO users (username, hash, cash) VALUES (?, ?, 10000)', (username, hash))
        self.conn.commit()
        return self.c.lastrowid

    def set_id(self, id):
        self.id = id

    def get_balance(self):
        self.c.execute('SELECT cash FROM users WHERE id=?', (self.id,))
        return self.c.fetchone()

    def update_balance(self, new_balance):
        self.c.execute('UPDATE users SET cash=? WHERE id=?', (new_balance,self.id))
        self.conn.commit()

    def update_password(self, hash):
        self.c.execute('UPDATE users SET hash=? WHERE id=?', (hash, self.id))
        self.conn.commit()


class transactions_db:
    def __init__(self, user_id, conn):
        self.id = user_id
        self.conn = conn
        self.c = conn.cursor()

    def get_history(self):
        self.c.execute('SELECT * FROM transactions where user_id=?', (self.id))
        results = []
        for data in self.c.fetchall():
            col = {}
            col['type'] = data[1]
            col['symbol'] = data[2]
            col['price'] = data[3]
            col['shares'] = data[4]
            col['date_time'] = data[5]
            results.append(col)
        return results

    def insert(self, row):
        self.c.execute('INSERT INTO transactions VALUES (?,?,?,?,?,?)', (self.id,) + row)
        self.conn.commit()


class portfolio_db:
    def __init__(self, user_id, conn):
        self.id = user_id
        self.conn = conn
        self.c = conn.cursor()

    def get_holdings(self):
        self.c.execute('SELECT symbol, shares FROM portfolio WHERE user_id=?', (self.id,))
        results = []
        for data in self.c.fetchall():
            col = {}
            col['symbol'] = data[0]
            col['shares'] = data[1]
            results.append(col)
        return results

    def get_number_of_shares(self, symbol):
        self.c.execute('SELECT shares FROM portfolio WHERE user_id=? AND symbol=?', (self.id, symbol))
        return self.c.fetchone()

    def update_shares(self, shares, symbol):
        self.c.execute('UPDATE portfolio SET shares=? WHERE symbol=? AND user_id=?', (shares, symbol, self.id))
        self.conn.commit()

    def insert_shares(self, shares, symbol):
        self.c.execute('INSERT INTO portfolio VALUES (?,?,?)', (self.id, symbol, shares))
        self.conn.commit()