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@ -3,27 +3,31 @@
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Step 2: Application Setup Code |
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============================== |
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Now that the schema is in place, you can create the application module, |
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:file:`flaskr.py`. This file should be placed inside of the |
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:file:`flaskr/flaskr` folder. The first several lines of code in the |
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application module are the needed import statements. After that there will be a |
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few lines of configuration code. For small applications like ``flaskr``, it is |
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possible to drop the configuration directly into the module. However, a cleaner |
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solution is to create a separate ``.ini`` or ``.py`` file, load that, and |
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import the values from there. |
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Next, we will create the application module, :file:`flaskr.py`. Just like the |
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:file:`schema.sql` file you created in the previous step, this file should be |
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placed inside of the :file:`flaskr/flaskr` folder. |
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For this tutorial, all the Python code we use will be put into this file |
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(except for one line in ``__init__.py``, and any testing or optional files you |
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decide to create). |
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The first several lines of code in the application module are the needed import |
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statements. After that there will be a few lines of configuration code. |
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For small applications like ``flaskr``, it is possible to drop the configuration |
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directly into the module. However, a cleaner solution is to create a separate |
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``.py`` file, load that, and import the values from there. |
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Here are the import statements (in :file:`flaskr.py`):: |
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# all the imports |
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import os |
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import sqlite3 |
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from flask import Flask, request, session, g, redirect, url_for, abort, \ |
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render_template, flash |
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The next couple lines will create the actual application instance and |
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initialize it with the config from the same file in :file:`flaskr.py`: |
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from flask import (Flask, request, session, g, redirect, url_for, abort, |
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render_template, flash) |
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.. sourcecode:: python |
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The next couple lines will create the actual application instance and |
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initialize it with the config from the same file in :file:`flaskr.py`:: |
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app = Flask(__name__) # create the application instance :) |
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app.config.from_object(__name__) # load config from this file , flaskr.py |
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@ -37,8 +41,8 @@ initialize it with the config from the same file in :file:`flaskr.py`:
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)) |
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app.config.from_envvar('FLASKR_SETTINGS', silent=True) |
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The :class:`~flask.Config` object works similarly to a dictionary, so it can be |
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updated with new values. |
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In the above code, the :class:`~flask.Config` object works similarly to a |
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dictionary, so it can be updated with new values. |
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.. admonition:: Database Path |
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@ -58,15 +62,15 @@ updated with new values.
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Usually, it is a good idea to load a separate, environment-specific |
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configuration file. Flask allows you to import multiple configurations and it |
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will use the setting defined in the last import. This enables robust |
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configuration setups. :meth:`~flask.Config.from_envvar` can help achieve this. |
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.. sourcecode:: python |
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configuration setups. :meth:`~flask.Config.from_envvar` can help achieve |
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this. :: |
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app.config.from_envvar('FLASKR_SETTINGS', silent=True) |
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Simply define the environment variable :envvar:`FLASKR_SETTINGS` that points to |
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a config file to be loaded. The silent switch just tells Flask to not complain |
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if no such environment key is set. |
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If you want to do this (not required for this tutorial) simply define the |
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environment variable :envvar:`FLASKR_SETTINGS` that points to a config file |
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to be loaded. The silent switch just tells Flask to not complain if no such |
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environment key is set. |
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In addition to that, you can use the :meth:`~flask.Config.from_object` |
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method on the config object and provide it with an import name of a |
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@ -76,22 +80,22 @@ that in all cases, only variable names that are uppercase are considered.
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The ``SECRET_KEY`` is needed to keep the client-side sessions secure. |
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Choose that key wisely and as hard to guess and complex as possible. |
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Lastly, you will add a method that allows for easy connections to the |
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specified database. This can be used to open a connection on request and |
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also from the interactive Python shell or a script. This will come in |
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handy later. You can create a simple database connection through SQLite and |
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then tell it to use the :class:`sqlite3.Row` object to represent rows. |
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This allows the rows to be treated as if they were dictionaries instead of |
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tuples. |
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.. sourcecode:: python |
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Lastly, add a method that allows for easy connections to the specified |
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database. :: |
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def connect_db(): |
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"""Connects to the specific database.""" |
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rv = sqlite3.connect(app.config['DATABASE']) |
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rv.row_factory = sqlite3.Row |
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return rv |
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This can be used to open a connection on request and also from the |
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interactive Python shell or a script. This will come in handy later. |
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You can create a simple database connection through SQLite and then tell |
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it to use the :class:`sqlite3.Row` object to represent rows. This allows |
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the rows to be treated as if they were dictionaries instead of tuples. |
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In the next section you will see how to run the application. |
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Continue with :ref:`tutorial-packaging`. |
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