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Minor edits to tutorial for clarity. (#2330)

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Dave Morse 7 years ago committed by David Lord
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50c6df7098
  1. 3
      docs/tutorial/dbcon.rst
  2. 31
      docs/tutorial/dbinit.rst
  3. 14
      docs/tutorial/folders.rst
  4. 18
      docs/tutorial/index.rst
  5. 50
      docs/tutorial/packaging.rst
  6. 66
      docs/tutorial/setup.rst
  7. 3
      docs/tutorial/templates.rst
  8. 3
      docs/tutorial/views.rst

3
docs/tutorial/dbcon.rst

@ -3,6 +3,9 @@
Step 4: Database Connections
----------------------------
Let's continue building our code in the ``flaskr.py`` file.
(Scroll to the end of the page for more about project layout.)
You currently have a function for establishing a database connection with
`connect_db`, but by itself, it is not particularly useful. Creating and
closing database connections all the time is very inefficient, so you will

31
docs/tutorial/dbinit.rst

@ -9,31 +9,37 @@ systems need a schema that tells them how to store that information.
Before starting the server for the first time, it's important to create
that schema.
Such a schema can be created by piping the ``schema.sql`` file into the
`sqlite3` command as follows::
Such a schema could be created by piping the ``schema.sql`` file into the
``sqlite3`` command as follows::
sqlite3 /tmp/flaskr.db < schema.sql
The downside of this is that it requires the ``sqlite3`` command to be
installed, which is not necessarily the case on every system. This also
requires that you provide the path to the database, which can introduce
errors. It's a good idea to add a function that initializes the database
for you, to the application.
However, the downside of this is that it requires the ``sqlite3`` command
to be installed, which is not necessarily the case on every system. This
also requires that you provide the path to the database, which can introduce
errors.
To do this, you can create a function and hook it into a :command:`flask`
command that initializes the database. For now just take a look at the
code segment below. A good place to add this function, and command, is
just below the `connect_db` function in :file:`flaskr.py`::
Instead of the ``sqlite3`` command above, it's a good idea to add a function
to our application that initializes the database for you. To do this, you
can create a function and hook it into a :command:`flask` command that
initializes the database.
Take a look at the code segment below. A good place to add this function,
and command, is just below the ``connect_db`` function in :file:`flaskr.py`::
def init_db():
db = get_db()
with app.open_resource('schema.sql', mode='r') as f:
db.cursor().executescript(f.read())
db.commit()
@app.cli.command('initdb')
def initdb_command():
"""Initializes the database."""
init_db()
print('Initialized the database.')
@ -59,7 +65,8 @@ On that cursor, there is a method to execute a complete script. Finally, you
only have to commit the changes. SQLite3 and other transactional
databases will not commit unless you explicitly tell it to.
Now, it is possible to create a database with the :command:`flask` script::
Now, in a terminal, from the application root directory :file:`flaskr/` it is
possible to create a database with the :command:`flask` script::
flask initdb
Initialized the database.

14
docs/tutorial/folders.rst

@ -3,8 +3,11 @@
Step 0: Creating The Folders
============================
Before getting started, you will need to create the folders needed for this
application::
It is recommended to install your Flask application within a virtualenv. Please
read the :ref:`installation` section to set up your environment.
Now that you have installed Flask, you will need to create the folders required
for this tutorial. Your directory structure will look like this::
/flaskr
/flaskr
@ -13,9 +16,10 @@ application::
The application will be installed and run as Python package. This is the
recommended way to install and run Flask applications. You will see exactly
how to run ``flaskr`` later on in this tutorial. For now go ahead and create
the applications directory structure. In the next few steps you will be
creating the database schema as well as the main module.
how to run ``flaskr`` later on in this tutorial.
For now go ahead and create the applications directory structure. In the next
few steps you will be creating the database schema as well as the main module.
As a quick side note, the files inside of the :file:`static` folder are
available to users of the application via HTTP. This is the place where CSS and

18
docs/tutorial/index.rst

@ -3,19 +3,19 @@
Tutorial
========
You want to develop an application with Python and Flask? Here you have
the chance to learn by example. In this tutorial, we will create a simple
microblogging application. It only supports one user that can create
text-only entries and there are no feeds or comments, but it still
features everything you need to get started. We will use Flask and SQLite
as a database (which comes out of the box with Python) so there is nothing
else you need.
Learn by example to develop an application with Python and Flask.
In this tutorial, we will create a simple blogging application. It only
supports one user, only allows text entries, and has no feeds or comments.
While very simple, this example still features everything you need to get
started. In addition to Flask, we will use SQLite for the database, which is
built-in to Python, so there is nothing else you need.
If you want the full source code in advance or for comparison, check out
the `example source`_.
.. _example source:
https://github.com/pallets/flask/tree/master/examples/flaskr/
.. _example source: https://github.com/pallets/flask/tree/master/examples/flaskr/
.. toctree::
:maxdepth: 2

50
docs/tutorial/packaging.rst

@ -9,10 +9,10 @@ tutorial you will see exactly how to extend the ``flask`` command line
interface (CLI).
A useful pattern to manage a Flask application is to install your app
following the `Python Packaging Guide`_. Presently this involves
creating two new files; :file:`setup.py` and :file:`MANIFEST.in` in the
projects root directory. You also need to add an :file:`__init__.py`
file to make the :file:`flaskr/flaskr` directory a package. After these
following the `Python Packaging Guide`_. Presently this involves
creating two new files; :file:`setup.py` and :file:`MANIFEST.in` in the
projects root directory. You also need to add an :file:`__init__.py`
file to make the :file:`flaskr/flaskr` directory a package. After these
changes, your code structure should be::
/flaskr
@ -25,9 +25,7 @@ changes, your code structure should be::
setup.py
MANIFEST.in
The content of the ``setup.py`` file for ``flaskr`` is:
.. sourcecode:: python
Create the ``setup.py`` file for ``flaskr`` with the following content::
from setuptools import setup
@ -43,53 +41,53 @@ The content of the ``setup.py`` file for ``flaskr`` is:
When using setuptools, it is also necessary to specify any special files
that should be included in your package (in the :file:`MANIFEST.in`).
In this case, the static and templates directories need to be included,
as well as the schema. Create the :file:`MANIFEST.in` and add the
following lines::
as well as the schema.
Create the :file:`MANIFEST.in` and add the following lines::
graft flaskr/templates
graft flaskr/static
include flaskr/schema.sql
To simplify locating the application, add the following import statement
into this file, :file:`flaskr/__init__.py`:
.. sourcecode:: python
Next, to simplify locating the application, create the file,
:file:`flaskr/__init__.py` containing only the following import statement::
from .flaskr import app
This import statement brings the application instance into the top-level
of the application package. When it is time to run the application, the
Flask development server needs the location of the app instance. This
import statement simplifies the location process. Without it the export
statement a few steps below would need to be
This import statement brings the application instance into the top-level
of the application package. When it is time to run the application, the
Flask development server needs the location of the app instance. This
import statement simplifies the location process. Without the above
import statement, the export statement a few steps below would need to be
``export FLASK_APP=flaskr.flaskr``.
At this point you should be able to install the application. As usual, it
is recommended to install your Flask application within a `virtualenv`_.
With that said, go ahead and install the application with::
With that said, from the ``flaskr/`` directory, go ahead and install the
application with::
pip install --editable .
The above installation command assumes that it is run within the projects
root directory, `flaskr/`. The `editable` flag allows editing
source code without having to reinstall the Flask app each time you make
changes. The flaskr app is now installed in your virtualenv (see output
The above installation command assumes that it is run within the projects
root directory, ``flaskr/``. The ``editable`` flag allows editing
source code without having to reinstall the Flask app each time you make
changes. The flaskr app is now installed in your virtualenv (see output
of ``pip freeze``).
With that out of the way, you should be able to start up the application.
Do this with the following commands::
Do this on Mac or Linux with the following commands in ``flaskr/``::
export FLASK_APP=flaskr
export FLASK_DEBUG=true
flask run
(In case you are on Windows you need to use `set` instead of `export`).
(In case you are on Windows you need to use ``set`` instead of ``export``).
The :envvar:`FLASK_DEBUG` flag enables or disables the interactive debugger.
*Never leave debug mode activated in a production system*, because it will
allow users to execute code on the server!
You will see a message telling you that server has started along with
the address at which you can access it.
the address at which you can access it in a browser.
When you head over to the server in your browser, you will get a 404 error
because we don't have any views yet. That will be addressed a little later,

66
docs/tutorial/setup.rst

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

3
docs/tutorial/templates.rst

@ -15,7 +15,8 @@ escaped with their XML equivalents.
We are also using template inheritance which makes it possible to reuse
the layout of the website in all pages.
Put the following templates into the :file:`templates` folder:
Create the follwing three HTML files and place them in the
:file:`templates` folder:
.. _Jinja2: http://jinja.pocoo.org/docs/templates

3
docs/tutorial/views.rst

@ -4,7 +4,8 @@ Step 6: The View Functions
==========================
Now that the database connections are working, you can start writing the
view functions. You will need four of them:
view functions. You will need four of them; Show Entries, Add New Entry,
Login and Logout. Add the following code snipets to :file:`flaskr.py`.
Show Entries
------------

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