Create database with sqlalchemy for flask web app

db_create.py

#!flask/bin/python
from migrate.versioning import api
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
import os.path

basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)
db = SQLAlchemy(app)

SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(basedir, 'app.db')
SQLALCHEMY_MIGRATE_REPO = os.path.join(basedir, 'db_repository')

db.create_all()
if not os.path.exists(SQLALCHEMY_MIGRATE_REPO):
    api.create(SQLALCHEMY_MIGRATE_REPO, 'database repository')
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
else:
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO, api.version(SQLALCHEMY_MIGRATE_REPO))