Step 3: データベースを作成する

Flaskrは、リレーショナルデータベースの機能を使っています。その為データベースを 作成するためにスキーマが必要になります。

その為に schema.sql ファイルにSQLite3用のコマンドを記述しておきます:

sqlite3 /tmp/flaskr.db < schema.sql

If you want to do that, you first have to import the contextlib.closing() function from the contextlib package. If you want to use Python 2.5 it’s also necessary to enable the with statement first (__future__ imports must be the very first import):

from __future__ import with_statement
from contextlib import closing

Next we can create a function called init_db that initializes the database. For this we can use the connect_db function we defined earlier. Just add that function below the connect_db function:

def init_db():
    with closing(connect_db()) as db:
        with app.open_resource('schema.sql') as f:
            db.cursor().executescript(f.read())
        db.commit()

The closing() helper function allows us to keep a connection open for the duration of the with block. The open_resource() method of the application object supports that functionality out of the box, so it can be used in the with block directly. This function opens a file from the resource location (your flaskr folder) and allows you to read from it. We are using this here to execute a script on the database connection.

When we connect to a database we get a connection object (here called db) that can give us a cursor. On that cursor there is a method to execute a complete script. Finally we only have to commit the changes. SQLite 3 and other transactional databases will not commit unless you explicitly tell it to.

Now it is possible to create a database by starting up a Python shell and importing and calling that function:

>>> from flaskr import init_db
>>> init_db()

Troubleshooting

If you get an exception later that a table cannot be found check that you did call the init_db function and that your table names are correct (singular vs. plural for example).

Step 4: データベースの利用

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