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Writing your first Django app, part 1
Let's learn by example.
Throughout this tutorial, we'll walk you through the creation of a basic
poll application.
It'll consist of two parts:
* A public site that lets people view polls and vote in them.
* An admin site that lets you add, change, and delete polls.
We'll assume you have :doc:`Django installed </intro/install>` already. You can
tell Django is installed and which version by running the following command:
.. code-block:: console
$ python -c "import django; print(django.get_version())"
If Django is installed, you should see the version of your installation. If it
isn't, you'll get an error telling "No module named django".
This tutorial is written for Django |version| and Python 3.4 or later. If the
Django version doesn't match, you can refer to the tutorial for your version
of Django by using the version switcher at the bottom right corner of this
page, or update Django to the newest version. If you are still using Python
2.7, you will need to adjust the code samples slightly, as described in
See :doc:`How to install Django </topics/install>` for advice on how to remove
older versions of Django and install a newer one.
.. admonition:: Where to get help:
If you're having trouble going through this tutorial, please post a message
to |django-users| or drop by `#django on
<irc://>`_ to chat with other Django users who might
be able to help.
Creating a project
If this is your first time using Django, you'll have to take care of some
initial setup. Namely, you'll need to auto-generate some code that establishes a
Django :term:`project` -- a collection of settings for an instance of Django,
including database configuration, Django-specific options and
application-specific settings.
From the command line, ``cd`` into a directory where you'd like to store your
code, then run the following command:
.. code-block:: console
$ django-admin startproject mysite
This will create a ``mysite`` directory in your current directory. If it didn't
work, see :ref:`troubleshooting-django-admin`.
.. note::
You'll need to avoid naming projects after built-in Python or Django
components. In particular, this means you should avoid using names like
``django`` (which will conflict with Django itself) or ``test`` (which
conflicts with a built-in Python package).
.. admonition:: Where should this code live?
If your background is in plain old PHP (with no use of modern frameworks),
you're probably used to putting code under the Web server's document root
(in a place such as ``/var/www``). With Django, you don't do that. It's
not a good idea to put any of this Python code within your Web server's
document root, because it risks the possibility that people may be able
to view your code over the Web. That's not good for security.
Put your code in some directory **outside** of the document root, such as
Let's look at what :djadmin:`startproject` created::
These files are:
* The outer :file:`mysite/` root directory is just a container for your
project. Its name doesn't matter to Django; you can rename it to anything
you like.
* :file:``: A command-line utility that lets you interact with this
Django project in various ways. You can read all the details about
:file:`` in :doc:`/ref/django-admin`.
* The inner :file:`mysite/` directory is the actual Python package for your
project. Its name is the Python package name you'll need to use to import
anything inside it (e.g. ``mysite.urls``).
* :file:`mysite/`: An empty file that tells Python that this
directory should be considered a Python package. (Read `more about
packages`_ in the official Python docs if you're a Python beginner.)
* :file:`mysite/`: Settings/configuration for this Django
project. :doc:`/topics/settings` will tell you all about how settings
* :file:`mysite/`: The URL declarations for this Django project; a
"table of contents" of your Django-powered site. You can read more about
URLs in :doc:`/topics/http/urls`.
* :file:`mysite/`: An entry-point for WSGI-compatible web servers to
serve your project. See :doc:`/howto/deployment/wsgi/index` for more details.
.. _more about packages:
The development server
Let's verify your Django project works. Change into the outer :file:`mysite` directory, if
you haven't already, and run the following commands:
.. code-block:: console
$ python runserver
You'll see the following output on the command line:
.. parsed-literal::
Performing system checks...
System check identified no issues (0 silenced).
You have unapplied migrations; your app may not work properly until they are applied.
Run 'python migrate' to apply them.
|today| - 15:50:53
Django version |version|, using settings 'mysite.settings'
Starting development server at
Quit the server with CONTROL-C.
.. note::
Ignore the warning about unapplied database migrations for now; we'll deal
with the database shortly.
You've started the Django development server, a lightweight Web server written
purely in Python. We've included this with Django so you can develop things
rapidly, without having to deal with configuring a production server -- such as
Apache -- until you're ready for production.
Now's a good time to note: **don't** use this server in anything resembling a
production environment. It's intended only for use while developing. (We're in
the business of making Web frameworks, not Web servers.)
Now that the server's running, visit with your Web
browser. You'll see a "Welcome to Django" page, in pleasant, light-blue pastel.
It worked!
.. admonition:: Changing the port
By default, the :djadmin:`runserver` command starts the development server
on the internal IP at port 8000.
If you want to change the server's port, pass
it as a command-line argument. For instance, this command starts the server
on port 8080:
.. code-block:: console
$ python runserver 8080
If you want to change the server's IP, pass it along with the port. So to
listen on all public IPs (useful if you want to show off your work on other
computers on your network), use:
.. code-block:: console
$ python runserver
Full docs for the development server can be found in the
:djadmin:`runserver` reference.
.. admonition:: Automatic reloading of :djadmin:`runserver`
The development server automatically reloads Python code for each request
as needed. You don't need to restart the server for code changes to take
effect. However, some actions like adding files don't trigger a restart,
so you'll have to restart the server in these cases.
Creating the Polls app
Now that your environment -- a "project" -- is set up, you're set to start
doing work.
Each application you write in Django consists of a Python package that follows
a certain convention. Django comes with a utility that automatically generates
the basic directory structure of an app, so you can focus on writing code
rather than creating directories.
.. admonition:: Projects vs. apps
What's the difference between a project and an app? An app is a Web
application that does something -- e.g., a Weblog system, a database of
public records or a simple poll app. A project is a collection of
configuration and apps for a particular Web site. A project can contain
multiple apps. An app can be in multiple projects.
Your apps can live anywhere on your `Python path`_. In this tutorial, we'll
create our poll app right next to your :file:`` file so that it can be
imported as its own top-level module, rather than a submodule of ``mysite``.
To create your app, make sure you're in the same directory as :file:``
and type this command:
.. code-block:: console
$ python startapp polls
That'll create a directory :file:`polls`, which is laid out like this::
This directory structure will house the poll application.
.. _`Python path`:
Write your first view
Let's write the first view. Open the file ``polls/``
and put the following Python code in it:
.. snippet::
:filename: polls/
from django.http import HttpResponse
def index(request):
return HttpResponse("Hello, world. You're at the polls index.")
This is the simplest view possible in Django. To call the view, we need to map
it to a URL - and for this we need a URLconf.
To create a URLconf in the polls directory, create a file called ````.
Your app directory should now look like::
In the ``polls/`` file include the following code:
.. snippet::
:filename: polls/
from django.conf.urls import url
from . import views
urlpatterns = [
url(r'^$', views.index, name='index'),
The next step is to point the root URLconf at the ``polls.urls`` module. In
``mysite/``, add an import for ``django.conf.urls.include`` and insert
an :func:`~django.conf.urls.include` in the ``urlpatterns`` list, so you have:
.. snippet::
:filename: mysite/
from django.conf.urls import include, url
from django.contrib import admin
urlpatterns = [
url(r'^polls/', include('polls.urls')),
.. admonition:: Doesn't match what you see?
If you're seeing ``include(`` instead of just
````, you're probably using a version of Django that
doesn't match this tutorial version. You'll want to either switch to the
older tutorial or the newer Django version.
You have now wired an ``index`` view into the URLconf. Lets verify it's
working, run the following command:
.. code-block:: console
$ python runserver
Go to http://localhost:8000/polls/ in your browser, and you should see the
text "*Hello, world. You're at the polls index.*", which you defined in the
``index`` view.
The :func:`~django.conf.urls.url` function is passed four arguments, two
required: ``regex`` and ``view``, and two optional: ``kwargs``, and ``name``.
At this point, it's worth reviewing what these arguments are for.
:func:`~django.conf.urls.url` argument: regex
The term "regex" is a commonly used short form meaning "regular expression",
which is a syntax for matching patterns in strings, or in this case, url
patterns. Django starts at the first regular expression and makes its way down
the list, comparing the requested URL against each regular expression until it
finds one that matches.
Note that these regular expressions do not search GET and POST parameters, or
the domain name. For example, in a request to
````, the URLconf will look for ``myapp/``. In a
request to ````, the URLconf will also
look for ``myapp/``.
If you need help with regular expressions, see `Wikipedia's entry`_ and the
documentation of the :mod:`re` module. Also, the O'Reilly book "Mastering
Regular Expressions" by Jeffrey Friedl is fantastic. In practice, however,
you don't need to be an expert on regular expressions, as you really only need
to know how to capture simple patterns. In fact, complex regexes can have poor
lookup performance, so you probably shouldn't rely on the full power of regexes.
Finally, a performance note: these regular expressions are compiled the first
time the URLconf module is loaded. They're super fast (as long as the lookups
aren't too complex as noted above).
.. _Wikipedia's entry:
:func:`~django.conf.urls.url` argument: view
When Django finds a regular expression match, Django calls the specified view
function, with an :class:`~django.http.HttpRequest` object as the first
argument and any “captured” values from the regular expression as other
arguments. If the regex uses simple captures, values are passed as positional
arguments; if it uses named captures, values are passed as keyword arguments.
We'll give an example of this in a bit.
:func:`~django.conf.urls.url` argument: kwargs
Arbitrary keyword arguments can be passed in a dictionary to the target view. We
aren't going to use this feature of Django in the tutorial.
:func:`~django.conf.urls.url` argument: name
Naming your URL lets you refer to it unambiguously from elsewhere in Django
especially templates. This powerful feature allows you to make global changes
to the url patterns of your project while only touching a single file.
When you're comfortable with the basic request and response flow, read
:doc:`part 2 of this tutorial </intro/tutorial02>` to start working with the
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