create_tables.py

# -*- coding: utf-8 -*-
# @Author: udacity
# @Date:   2020-12-09 21:49:31
# @Last Modified by:   anh-tuan.vu
# @Last Modified time: 2020-12-12 00:58:55

import psycopg2
from sql_queries import create_table_queries, drop_table_queries


def create_database():
    """
    - Creates and connects to the sparkifydb
    - Returns the connection and cursor to sparkifydb
    """
    # connect to default database
    conn = psycopg2.connect("host=127.0.0.1 dbname=studentdb \
        user=student password=student")
    conn.set_session(autocommit=True)
    cur = conn.cursor()

    # create sparkify database with UTF8 encoding
    cur.execute("DROP DATABASE IF EXISTS sparkifydb")
    cur.execute("CREATE DATABASE sparkifydb \
        WITH ENCODING 'utf8' TEMPLATE template0")

    # close connection to default database
    conn.close()

    # connect to sparkify database
    conn = psycopg2.connect("host=127.0.0.1 dbname=sparkifydb \
        user=student password=student")
    cur = conn.cursor()

    return cur, conn


def drop_tables(cur, conn):
    """
    Drops each table using the queries in `drop_table_queries` list.
    """
    for query in drop_table_queries:
        cur.execute(query)
        conn.commit()


def create_tables(cur, conn):
    """
    Creates each table using the queries in `create_table_queries` list.
    """
    for query in create_table_queries:
        cur.execute(query)
        conn.commit()


def main():
    """
    - Drops (if exists) and Creates the sparkify database.

    - Establishes connection with the sparkify database and gets
    cursor to it.

    - Drops all the tables.

    - Creates all tables needed.

    - Finally, closes the connection.
    """
    cur, conn = create_database()

    drop_tables(cur, conn)
    create_tables(cur, conn)

    conn.close()


if __name__ == "__main__":
    main()