forked from orbit-oss/flask
17d4cb3828
* Converts example/flaskr to have a setup.py Makes the flaskr app easier to run, ex. workflow: - pip install --editable . - export FLASK_APP=flaskr.flaskr - flask initdb - flask run Testing is also easier now: - python setup.py test * Fixed an import error in flaskr/tests - the statement `import flaskr` caused errors in python3 - `from . import flaskr` fixes the issue in 2.7.11 and 3.5.1 * Better project structure and updates the docs - Re-factors *flaskr*'s project structure a bit - Updates docs to make sense with the new structure - Adds a new step about installing Flask apps with setuptools - Switches first-person style writing to second-person (reads better IMO) - Adds segments in *testing.rst* for running tests with setuptools * Remove __init__.py from tests - py.test recommends not using __init__.py * Fix testing import errors
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.. _tutorial-dbinit:
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Step 5: Creating The Database
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=============================
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As outlined earlier, Flaskr is a database powered application, and more
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precisely, it is an application powered by a relational database system. Such
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systems need a schema that tells them how to store that information.
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Before starting the server for the first time, it's important to create
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that schema.
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Such a schema can be created by piping the ``schema.sql`` file into the
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`sqlite3` command as follows::
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sqlite3 /tmp/flaskr.db < schema.sql
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The downside of this is that it requires the ``sqlite3`` command to be
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installed, which is not necessarily the case on every system. This also
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requires that you provide the path to the database, which can introduce
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errors. It's a good idea to add a function that initializes the database
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for you, to the application.
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To do this, you can create a function and hook it into a :command:`flask`
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command that initializes the database. For now just take a look at the
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code segment below. A good place to add this function, and command, is
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just below the `connect_db` function in :file:`flaskr.py`::
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def init_db():
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db = get_db()
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with app.open_resource('schema.sql', mode='r') as f:
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db.cursor().executescript(f.read())
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db.commit()
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@app.cli.command('initdb')
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def initdb_command():
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"""Initializes the database."""
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init_db()
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print 'Initialized the database.'
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The ``app.cli.command()`` decorator registers a new command with the
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:command:`flask` script. When the command executes, Flask will automatically
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create an application context which is bound to the right application.
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Within the function, you can then access :attr:`flask.g` and other things as
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you might expect. When the script ends, the application context tears down
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and the database connection is released.
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You will want to keep an actual function around that initializes the database,
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though, so that we can easily create databases in unit tests later on. (For
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more information see :ref:`testing`.)
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The :func:`~flask.Flask.open_resource` method of the application object
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is a convenient helper function that will open a resource that the
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application provides. This function opens a file from the resource
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location (the :file:`flaskr/flaskr` folder) and allows you to read from it.
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It is used in this example to execute a script on the database connection.
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The connection object provided by SQLite can give you a cursor object.
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On that cursor, there is a method to execute a complete script. Finally, you
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only have to commit the changes. SQLite3 and other transactional
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databases will not commit unless you explicitly tell it to.
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Now, it is possible to create a database with the :command:`flask` script::
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flask initdb
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Initialized the database.
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.. admonition:: Troubleshooting
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If you get an exception later on stating that a table cannot be found, check
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that you did execute the ``initdb`` command and that your table names are
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correct (singular vs. plural, for example).
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Continue with :ref:`tutorial-views`
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