import os
import datetime as dt
from sqlite3 import dbapi2 as sqlite3
from flask import Flask, request, session, g, redirect, url_for, abort, \
render_template, flash

the application object from the main Flask class

app = Flask(name)

override config from environment variable

app.config.update(dict(
DATABASE=os.path.join(app.root_path, ‘tradechat.db’),

the SQLite3 database file (“TC database”)

DEBUG=True,
SECRET_KEY=‘secret_key’,

use secure key here for real applications

))
app.config.from_envvar(‘TC_SETTINGS’, silent=True)

do not complain if no config file exists

def connect_db():
”’ Connects to the TC database.”’
rv = sqlite3.connect(app.config[‘DATABASE’])
rv.row_factory = sqlite3.Row
return rv

def get_db():
”’ Opens a new connection to the TC database. ”’
if not hasattr(g, ‘sqlite_db’):

open only if none exists yet

g.sqlite_db = connect_db()
return g.sqlite_db

def init_db():
”’ Creates the TC database tables.”’
with app.app_context():
db = get_db()
with app.open_resource(‘tables.sql’, mode=‘r’) as f:
db.cursor().executescript(f.read())

creates entries and users tables

db.commit()

@app.teardown_appcontext
def close_db(error):
”’ Closes the TC database at the end of the request. ”’
if hasattr(g, ‘sqlite_db’):
g.sqlite_db.close()

@app.route(‘/’)
def show_entries():
”’ Renders all entries of the TC database. ”’
db = get_db()
query = ‘select comment, user, time from comments order by id desc’
cursor = db.execute(query)
comments = cursor.fetchall()
return render_template(‘show_entries.html’, comments=comments)

@app.route(‘/register’, methods=[‘GET’, ‘POST’])
def register():
”’ Registers a new user in the TC database. ”’
error = None
if request.method == ‘POST’:
db = get_db()
if request.form[‘username’] == ” or request.form[‘password’] == ”:
error = ‘Provide both a username and a password.’

both fields have to be nonempty

else:
db.execute(‘insert into users (name, password) values (?, ?)’,
[request.form[‘username’], request.form[‘password’]])
db.commit()