mirror of
https://github.com/django/django.git
synced 2024-12-24 10:05:46 +00:00
336 lines
13 KiB
Plaintext
336 lines
13 KiB
Plaintext
=============================================
|
||
Advanced tutorial: How to write reusable apps
|
||
=============================================
|
||
|
||
This advanced tutorial begins where :doc:`Tutorial 7 </intro/tutorial07>`
|
||
left off. We'll be turning our web-poll into a standalone Python package
|
||
you can reuse in new projects and share with other people.
|
||
|
||
If you haven't recently completed Tutorials 1–7, we encourage you to review
|
||
these so that your example project matches the one described below.
|
||
|
||
Reusability matters
|
||
===================
|
||
|
||
It's a lot of work to design, build, test and maintain a web application. Many
|
||
Python and Django projects share common problems. Wouldn't it be great if we
|
||
could save some of this repeated work?
|
||
|
||
Reusability is the way of life in Python. `The Python Package Index (PyPI)
|
||
<https://pypi.org/>`_ has a vast range of packages you can use in your own
|
||
Python programs. Check out `Django Packages <https://djangopackages.org>`_ for
|
||
existing reusable apps you could incorporate in your project. Django itself is
|
||
also a normal Python package. This means that you can take existing Python
|
||
packages or Django apps and compose them into your own web project. You only
|
||
need to write the parts that make your project unique.
|
||
|
||
Let's say you were starting a new project that needed a polls app like the one
|
||
we've been working on. How do you make this app reusable? Luckily, you're well
|
||
on the way already. In :doc:`Tutorial 1 </intro/tutorial01>`, we saw how we
|
||
could decouple polls from the project-level URLconf using an ``include``.
|
||
In this tutorial, we'll take further steps to make the app easy to use in new
|
||
projects and ready to publish for others to install and use.
|
||
|
||
.. admonition:: Package? App?
|
||
|
||
A Python :term:`package` provides a way of grouping related Python code for
|
||
easy reuse. A package contains one or more files of Python code (also known
|
||
as "modules").
|
||
|
||
A package can be imported with ``import foo.bar`` or ``from foo import
|
||
bar``. For a directory (like ``polls``) to form a package, it must contain
|
||
a special file ``__init__.py``, even if this file is empty.
|
||
|
||
A Django *application* is a Python package that is specifically intended
|
||
for use in a Django project. An application may use common Django
|
||
conventions, such as having ``models``, ``tests``, ``urls``, and ``views``
|
||
submodules.
|
||
|
||
Later on we use the term *packaging* to describe the process of making a
|
||
Python package easy for others to install. It can be a little confusing, we
|
||
know.
|
||
|
||
Your project and your reusable app
|
||
==================================
|
||
|
||
After the previous tutorials, our project should look like this::
|
||
|
||
mysite/
|
||
manage.py
|
||
mysite/
|
||
__init__.py
|
||
settings.py
|
||
urls.py
|
||
asgi.py
|
||
wsgi.py
|
||
polls/
|
||
__init__.py
|
||
admin.py
|
||
apps.py
|
||
migrations/
|
||
__init__.py
|
||
0001_initial.py
|
||
models.py
|
||
static/
|
||
polls/
|
||
images/
|
||
background.gif
|
||
style.css
|
||
templates/
|
||
polls/
|
||
detail.html
|
||
index.html
|
||
results.html
|
||
tests.py
|
||
urls.py
|
||
views.py
|
||
templates/
|
||
admin/
|
||
base_site.html
|
||
|
||
You created ``mysite/templates`` in :doc:`Tutorial 7 </intro/tutorial07>`,
|
||
and ``polls/templates`` in :doc:`Tutorial 3 </intro/tutorial03>`. Now perhaps
|
||
it is clearer why we chose to have separate template directories for the
|
||
project and application: everything that is part of the polls application is in
|
||
``polls``. It makes the application self-contained and easier to drop into a
|
||
new project.
|
||
|
||
The ``polls`` directory could now be copied into a new Django project and
|
||
immediately reused. It's not quite ready to be published though. For that, we
|
||
need to package the app to make it easy for others to install.
|
||
|
||
.. _installing-reusable-apps-prerequisites:
|
||
|
||
Installing some prerequisites
|
||
=============================
|
||
|
||
The current state of Python packaging is a bit muddled with various tools. For
|
||
this tutorial, we're going to use setuptools_ to build our package. It's the
|
||
recommended packaging tool (merged with the ``distribute`` fork). We'll also be
|
||
using `pip`_ to install and uninstall it. You should install these
|
||
two packages now. If you need help, you can refer to :ref:`how to install
|
||
Django with pip<installing-official-release>`. You can install ``setuptools``
|
||
the same way.
|
||
|
||
.. _setuptools: https://pypi.org/project/setuptools/
|
||
.. _pip: https://pypi.org/project/pip/
|
||
|
||
Packaging your app
|
||
==================
|
||
|
||
Python *packaging* refers to preparing your app in a specific format that can
|
||
be easily installed and used. Django itself is packaged very much like
|
||
this. For a small app like polls, this process isn't too difficult.
|
||
|
||
#. First, create a parent directory for ``polls``, outside of your Django
|
||
project. Call this directory ``django-polls``.
|
||
|
||
.. admonition:: Choosing a name for your app
|
||
|
||
When choosing a name for your package, check resources like PyPI to avoid
|
||
naming conflicts with existing packages. It's often useful to prepend
|
||
``django-`` to your module name when creating a package to distribute.
|
||
This helps others looking for Django apps identify your app as Django
|
||
specific.
|
||
|
||
Application labels (that is, the final part of the dotted path to
|
||
application packages) *must* be unique in :setting:`INSTALLED_APPS`.
|
||
Avoid using the same label as any of the Django :doc:`contrib packages
|
||
</ref/contrib/index>`, for example ``auth``, ``admin``, or
|
||
``messages``.
|
||
|
||
#. Move the ``polls`` directory into the ``django-polls`` directory.
|
||
|
||
#. Create a file ``django-polls/README.rst`` with the following contents:
|
||
|
||
.. code-block:: rst
|
||
:caption: django-polls/README.rst
|
||
|
||
=====
|
||
Polls
|
||
=====
|
||
|
||
Polls is a Django app to conduct web-based polls. For each question,
|
||
visitors can choose between a fixed number of answers.
|
||
|
||
Detailed documentation is in the "docs" directory.
|
||
|
||
Quick start
|
||
-----------
|
||
|
||
1. Add "polls" to your INSTALLED_APPS setting like this::
|
||
|
||
INSTALLED_APPS = [
|
||
...
|
||
'polls',
|
||
]
|
||
|
||
2. Include the polls URLconf in your project urls.py like this::
|
||
|
||
path('polls/', include('polls.urls')),
|
||
|
||
3. Run ``python manage.py migrate`` to create the polls models.
|
||
|
||
4. Start the development server and visit http://127.0.0.1:8000/admin/
|
||
to create a poll (you'll need the Admin app enabled).
|
||
|
||
5. Visit http://127.0.0.1:8000/polls/ to participate in the poll.
|
||
|
||
#. Create a ``django-polls/LICENSE`` file. Choosing a license is beyond the
|
||
scope of this tutorial, but suffice it to say that code released publicly
|
||
without a license is *useless*. Django and many Django-compatible apps are
|
||
distributed under the BSD license; however, you're free to pick your own
|
||
license. Just be aware that your licensing choice will affect who is able
|
||
to use your code.
|
||
|
||
#. Next we'll create ``pyproject.toml``, ``setup.cfg``, and ``setup.py`` files
|
||
which detail how to build and install the app. A full explanation of these
|
||
files is beyond the scope of this tutorial, but the `setuptools
|
||
documentation <https://setuptools.readthedocs.io/en/latest/>`_ has a good
|
||
explanation. Create the ``django-polls/pyproject.toml``,
|
||
``django-polls/setup.cfg``, and ``django-polls/setup.py`` files with the
|
||
following contents:
|
||
|
||
.. code-block:: toml
|
||
:caption: django-polls/pyproject.toml
|
||
|
||
[build-system]
|
||
requires = ['setuptools>=40.8.0', 'wheel']
|
||
build-backend = 'setuptools.build_meta:__legacy__'
|
||
|
||
.. code-block:: ini
|
||
:caption: django-polls/setup.cfg
|
||
|
||
[metadata]
|
||
name = django-polls
|
||
version = 0.1
|
||
description = A Django app to conduct web-based polls.
|
||
long_description = file: README.rst
|
||
url = https://www.example.com/
|
||
author = Your Name
|
||
author_email = yourname@example.com
|
||
license = BSD-3-Clause # Example license
|
||
classifiers =
|
||
Environment :: Web Environment
|
||
Framework :: Django
|
||
Framework :: Django :: X.Y # Replace "X.Y" as appropriate
|
||
Intended Audience :: Developers
|
||
License :: OSI Approved :: BSD License
|
||
Operating System :: OS Independent
|
||
Programming Language :: Python
|
||
Programming Language :: Python :: 3
|
||
Programming Language :: Python :: 3 :: Only
|
||
Programming Language :: Python :: 3.8
|
||
Programming Language :: Python :: 3.9
|
||
Topic :: Internet :: WWW/HTTP
|
||
Topic :: Internet :: WWW/HTTP :: Dynamic Content
|
||
|
||
[options]
|
||
include_package_data = true
|
||
packages = find:
|
||
python_requires = >=3.8
|
||
install_requires =
|
||
Django >= X.Y # Replace "X.Y" as appropriate
|
||
|
||
.. code-block:: python
|
||
:caption: django-polls/setup.py
|
||
|
||
from setuptools import setup
|
||
|
||
setup()
|
||
|
||
#. Only Python modules and packages are included in the package by default. To
|
||
include additional files, we'll need to create a ``MANIFEST.in`` file. The
|
||
setuptools docs referred to in the previous step discuss this file in more
|
||
detail. To include the templates, the ``README.rst`` and our ``LICENSE``
|
||
file, create a file ``django-polls/MANIFEST.in`` with the following
|
||
contents:
|
||
|
||
.. code-block:: text
|
||
:caption: django-polls/MANIFEST.in
|
||
|
||
include LICENSE
|
||
include README.rst
|
||
recursive-include polls/static *
|
||
recursive-include polls/templates *
|
||
|
||
#. It's optional, but recommended, to include detailed documentation with your
|
||
app. Create an empty directory ``django-polls/docs`` for future
|
||
documentation. Add an additional line to ``django-polls/MANIFEST.in``::
|
||
|
||
recursive-include docs *
|
||
|
||
Note that the ``docs`` directory won't be included in your package unless
|
||
you add some files to it. Many Django apps also provide their documentation
|
||
online through sites like `readthedocs.org <https://readthedocs.org>`_.
|
||
|
||
#. Try building your package with ``python setup.py sdist`` (run from inside
|
||
``django-polls``). This creates a directory called ``dist`` and builds your
|
||
new package, ``django-polls-0.1.tar.gz``.
|
||
|
||
For more information on packaging, see Python's `Tutorial on Packaging and
|
||
Distributing Projects
|
||
<https://packaging.python.org/tutorials/packaging-projects/>`_.
|
||
|
||
Using your own package
|
||
======================
|
||
|
||
Since we moved the ``polls`` directory out of the project, it's no longer
|
||
working. We'll now fix this by installing our new ``django-polls`` package.
|
||
|
||
.. admonition:: Installing as a user library
|
||
|
||
The following steps install ``django-polls`` as a user library. Per-user
|
||
installs have a lot of advantages over installing the package system-wide,
|
||
such as being usable on systems where you don't have administrator access
|
||
as well as preventing the package from affecting system services and other
|
||
users of the machine.
|
||
|
||
Note that per-user installations can still affect the behavior of system
|
||
tools that run as that user, so using a virtual environment is a more robust
|
||
solution (see below).
|
||
|
||
#. To install the package, use pip (you already :ref:`installed it
|
||
<installing-reusable-apps-prerequisites>`, right?)::
|
||
|
||
python -m pip install --user django-polls/dist/django-polls-0.1.tar.gz
|
||
|
||
#. With luck, your Django project should now work correctly again. Run the
|
||
server again to confirm this.
|
||
|
||
#. To uninstall the package, use pip::
|
||
|
||
python -m pip uninstall django-polls
|
||
|
||
Publishing your app
|
||
===================
|
||
|
||
Now that we've packaged and tested ``django-polls``, it's ready to share with
|
||
the world! If this wasn't just an example, you could now:
|
||
|
||
* Email the package to a friend.
|
||
|
||
* Upload the package on your website.
|
||
|
||
* Post the package on a public repository, such as `the Python Package Index
|
||
(PyPI)`_. `packaging.python.org <https://packaging.python.org>`_ has `a good
|
||
tutorial <https://packaging.python.org/tutorials/packaging-projects/#uploading-the-distribution-archives>`_
|
||
for doing this.
|
||
|
||
Installing Python packages with a virtual environment
|
||
=====================================================
|
||
|
||
Earlier, we installed the polls app as a user library. This has some
|
||
disadvantages:
|
||
|
||
* Modifying the user libraries can affect other Python software on your system.
|
||
|
||
* You won't be able to run multiple versions of this package (or others with
|
||
the same name).
|
||
|
||
Typically, these situations only arise once you're maintaining several Django
|
||
projects. When they do, the best solution is to use :doc:`venv
|
||
<python:tutorial/venv>`. This tool allows you to maintain multiple isolated
|
||
Python environments, each with its own copy of the libraries and package
|
||
namespace.
|