app.py

import json
from flask import Flask
import psycopg2
import os

app = Flask(__name__)

if 'POSTGRES_PASSWORD_FILE' in os.environ:
   with open(os.environ['POSTGRES_PASSWORD_FILE'], 'r') as f:
       password = f.read().strip()
else:
   password = os.environ['POSTGRES_PASSWORD']

@app.route('/')
def hello_world():
    return 'Hello, Dockers!!!'


@app.route('/widgets')
def get_widgets():
    with psycopg2.connect(host="db", user="postgres", password=password, database="example") as conn:
        with conn.cursor() as cur:
            cur.execute("SELECT * FROM widgets")
            row_headers = [x[0] for x in cur.description]
            results = cur.fetchall()
    conn.close()

    json_data = [dict(zip(row_headers, result)) for result in results]
    return json.dumps(json_data)


@app.route('/initdb')
def db_init():
    conn = psycopg2.connect(host="db", user="postgres", password=password)
    conn.set_session(autocommit=True)
    with conn.cursor() as cur:
        cur.execute("DROP DATABASE IF EXISTS example")
        cur.execute("CREATE DATABASE example")
    conn.close()

    with psycopg2.connect(host="db", user="postgres", password=password, database="example") as conn:
        with conn.cursor() as cur:
            cur.execute("DROP TABLE IF EXISTS widgets")
            cur.execute("CREATE TABLE widgets (name VARCHAR(255), description VARCHAR(255))")
    conn.close()

    return 'init database'


if __name__ == "__main__":
    app.run(host='0.0.0.0')