diff options
Diffstat (limited to 'app/static/doc/flask-docs/_sources/patterns/sqlite3.txt')
| -rw-r--r-- | app/static/doc/flask-docs/_sources/patterns/sqlite3.txt | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/app/static/doc/flask-docs/_sources/patterns/sqlite3.txt b/app/static/doc/flask-docs/_sources/patterns/sqlite3.txt deleted file mode 100644 index 0d02e46..0000000 --- a/app/static/doc/flask-docs/_sources/patterns/sqlite3.txt +++ /dev/null @@ -1,119 +0,0 @@ -.. _sqlite3: - -Using SQLite 3 with Flask -========================= - -In Flask you can implement the opening of database connections at the -beginning of the request and closing at the end with the -:meth:`~flask.Flask.before_request` and :meth:`~flask.Flask.teardown_request` -decorators in combination with the special :class:`~flask.g` object. - -So here is a simple example of how you can use SQLite 3 with Flask:: - - import sqlite3 - from flask import g - - DATABASE = '/path/to/database.db' - - def connect_db(): - return sqlite3.connect(DATABASE) - - @app.before_request - def before_request(): - g.db = connect_db() - - @app.teardown_request - def teardown_request(exception): - if hasattr(g, 'db'): - g.db.close() - -.. note:: - - Please keep in mind that the teardown request functions are always - executed, even if a before-request handler failed or was never - executed. Because of this we have to make sure here that the database - is there before we close it. - -Connect on Demand ------------------ - -The downside of this approach is that this will only work if Flask -executed the before-request handlers for you. If you are attempting to -use the database from a script or the interactive Python shell you would -have to do something like this:: - - with app.test_request_context(): - app.preprocess_request() - # now you can use the g.db object - -In order to trigger the execution of the connection code. You won't be -able to drop the dependency on the request context this way, but you could -make it so that the application connects when necessary:: - - def get_connection(): - db = getattr(g, '_db', None) - if db is None: - db = g._db = connect_db() - return db - -Downside here is that you have to use ``db = get_connection()`` instead of -just being able to use ``g.db`` directly. - -.. _easy-querying: - -Easy Querying -------------- - -Now in each request handling function you can access `g.db` to get the -current open database connection. To simplify working with SQLite, a -helper function can be useful:: - - def query_db(query, args=(), one=False): - cur = g.db.execute(query, args) - rv = [dict((cur.description[idx][0], value) - for idx, value in enumerate(row)) for row in cur.fetchall()] - return (rv[0] if rv else None) if one else rv - -This handy little function makes working with the database much more -pleasant than it is by just using the raw cursor and connection objects. - -Here is how you can use it:: - - for user in query_db('select * from users'): - print user['username'], 'has the id', user['user_id'] - -Or if you just want a single result:: - - user = query_db('select * from users where username = ?', - [the_username], one=True) - if user is None: - print 'No such user' - else: - print the_username, 'has the id', user['user_id'] - -To pass variable parts to the SQL statement, use a question mark in the -statement and pass in the arguments as a list. Never directly add them to -the SQL statement with string formatting because this makes it possible -to attack the application using `SQL Injections -<http://en.wikipedia.org/wiki/SQL_injection>`_. - -Initial Schemas ---------------- - -Relational databases need schemas, so applications often ship a -`schema.sql` file that creates the database. It's a good idea to provide -a function that creates the database based on that schema. This function -can do that for you:: - - from contextlib import closing - - def init_db(): - with closing(connect_db()) as db: - with app.open_resource('schema.sql') as f: - db.cursor().executescript(f.read()) - db.commit() - -You can then create such a database from the python shell: - ->>> from yourapplication import init_db ->>> init_db() |