{"title":"Advanced tutorial: How to write reusable apps","version":"5.0","locale":"en","docname":"intro/reusable-apps","url":"/en/5.0/intro/reusable-apps/","canonical":"https://djangodocs.dev/en/5.0/intro/reusable-apps/","summary":"This advanced tutorial begins where Tutorial 8 left off. We’ll be turning our web-poll into a standalone Python package you can reuse in new projects and share with…","html":"

Advanced tutorial: How to write reusable appsLink to this heading#

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This advanced tutorial begins where Tutorial 8\nleft off. We’ll be turning our web-poll into a standalone Python package\nyou can reuse in new projects and share with other people.

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If you haven’t recently completed Tutorials 1–7, we encourage you to review\nthese so that your example project matches the one described below.

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Reusability mattersLink to this heading#

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It’s a lot of work to design, build, test and maintain a web application. Many\nPython and Django projects share common problems. Wouldn’t it be great if we\ncould save some of this repeated work?

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Reusability is the way of life in Python. The Python Package Index (PyPI) has a vast range of packages you can use in your own\nPython programs. Check out Django Packages for\nexisting reusable apps you could incorporate in your project. Django itself is\nalso a normal Python package. This means that you can take existing Python\npackages or Django apps and compose them into your own web project. You only\nneed to write the parts that make your project unique.

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Let’s say you were starting a new project that needed a polls app like the one\nwe’ve been working on. How do you make this app reusable? Luckily, you’re well\non the way already. In Tutorial 1, we saw how we\ncould decouple polls from the project-level URLconf using an include.\nIn this tutorial, we’ll take further steps to make the app easy to use in new\nprojects and ready to publish for others to install and use.

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Your project and your reusable appLink to this heading#

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After the previous tutorials, our project should look like this:

\n
Text
mysite/\n    manage.py\n    mysite/\n        __init__.py\n        settings.py\n        urls.py\n        asgi.py\n        wsgi.py\n    polls/\n        __init__.py\n        admin.py\n        apps.py\n        migrations/\n            __init__.py\n            0001_initial.py\n        models.py\n        static/\n            polls/\n                images/\n                    background.png\n                style.css\n        templates/\n            polls/\n                detail.html\n                index.html\n                results.html\n        tests.py\n        urls.py\n        views.py\n    templates/\n        admin/\n            base_site.html\n
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You created mysite/templates in Tutorial 7,\nand polls/templates in Tutorial 3. Now perhaps\nit is clearer why we chose to have separate template directories for the\nproject and application: everything that is part of the polls application is in\npolls. It makes the application self-contained and easier to drop into a\nnew project.

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The polls directory could now be copied into a new Django project and\nimmediately reused. It’s not quite ready to be published though. For that, we\nneed to package the app to make it easy for others to install.

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Installing some prerequisitesLink to this heading#

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The current state of Python packaging is a bit muddled with various tools. For\nthis tutorial, we’re going to use setuptools to build our package. It’s\nthe recommended packaging tool (merged with the distribute fork). We’ll\nalso be using pip to install and uninstall it. You should install these\ntwo packages now. If you need help, you can refer to how to install\nDjango with pip. You can install setuptools\nthe same way.

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Packaging your appLink to this heading#

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Python packaging refers to preparing your app in a specific format that can\nbe easily installed and used. Django itself is packaged very much like\nthis. For a small app like polls, this process isn’t too difficult.

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    \n

  1. First, create a parent directory for the package, outside of your Django\nproject. Call this directory django-polls.

    \n\n
    2. \n

  2. Move the polls directory into django-polls directory, and rename it\nto django_polls.

    3. \n

  3. Edit django_polls/apps.py so that name refers to the\nnew module name and add label to give a short name for\nthe app:

    \n
    django-polls/django_polls/apps.py
    \n
    Python
    from django.apps import AppConfig\n\n\nclass PollsConfig(AppConfig):\n    default_auto_field = "django.db.models.BigAutoField"\n    name = "django_polls"\n    label = "polls"\n
    \n
    4. \n

  4. Create a file django-polls/README.rst with the following contents:

    \n
    django-polls/README.rst
    \n
    Rst
    ============\ndjango-polls\n============\n\ndjango-polls is a Django app to conduct web-based polls. For each\nquestion, visitors can choose between a fixed number of answers.\n\nDetailed documentation is in the "docs" directory.\n\nQuick start\n-----------\n\n1. Add "polls" to your INSTALLED_APPS setting like this::\n\n    INSTALLED_APPS = [\n        ...,\n        "django_polls",\n    ]\n\n2. Include the polls URLconf in your project urls.py like this::\n\n    path("polls/", include("django_polls.urls")),\n\n3. Run ``python manage.py migrate`` to create the models.\n\n4. Start the development server and visit the admin to create a poll.\n\n5. Visit the ``/polls/`` URL to participate in the poll.\n
    \n
    5. \n

  5. Create a django-polls/LICENSE file. Choosing a license is beyond the\nscope of this tutorial, but suffice it to say that code released publicly\nwithout a license is useless. Django and many Django-compatible apps are\ndistributed under the BSD license; however, you’re free to pick your own\nlicense. Just be aware that your licensing choice will affect who is able\nto use your code.

    6. \n

  6. Next we’ll create pyproject.toml, setup.cfg, and setup.py files\nwhich detail how to build and install the app. A full explanation of these\nfiles is beyond the scope of this tutorial, but the setuptools\ndocumentation has a good\nexplanation. Create the django-polls/pyproject.toml,\ndjango-polls/setup.cfg, and django-polls/setup.py files with the\nfollowing contents:

    \n
    django-polls/pyproject.toml
    \n
    Toml
    [build-system]\nrequires = ['setuptools>=40.8.0']\nbuild-backend = 'setuptools.build_meta'\n
    \n
    django-polls/setup.cfg
    \n
    Ini
    [metadata]\nname = django-polls\nversion = 0.1\ndescription = A Django app to conduct web-based polls.\nlong_description = file: README.rst\nurl = https://www.example.com/\nauthor = Your Name\nauthor_email = yourname@example.com\nlicense = BSD-3-Clause  # Example license\nclassifiers =\n    Environment :: Web Environment\n    Framework :: Django\n    Framework :: Django :: X.Y  # Replace "X.Y" as appropriate\n    Intended Audience :: Developers\n    License :: OSI Approved :: BSD License\n    Operating System :: OS Independent\n    Programming Language :: Python\n    Programming Language :: Python :: 3\n    Programming Language :: Python :: 3 :: Only\n    Programming Language :: Python :: 3.10\n    Programming Language :: Python :: 3.11\n    Programming Language :: Python :: 3.12\n    Topic :: Internet :: WWW/HTTP\n    Topic :: Internet :: WWW/HTTP :: Dynamic Content\n\n[options]\ninclude_package_data = true\npackages = find:\npython_requires = >=3.10\ninstall_requires =\n    Django >= X.Y  # Replace "X.Y" as appropriate\n
    \n
    django-polls/setup.py
    \n
    Python
    from setuptools import setup\n\nsetup()\n
    \n
    7. \n

  7. Only Python modules and packages are included in the package by default. To\ninclude additional files, we’ll need to create a MANIFEST.in file. The\nsetuptools docs referred to in the previous step discuss this file in\nmore detail. To include the templates, the README.rst and our\nLICENSE file, create a file django-polls/MANIFEST.in with the\nfollowing contents:

    \n
    django-polls/MANIFEST.in
    \n
    Text
    include LICENSE\ninclude README.rst\nrecursive-include django_polls/static *\nrecursive-include django_polls/templates *\n
    \n
    8. \n

  8. It’s optional, but recommended, to include detailed documentation with your\napp. Create an empty directory django-polls/docs for future\ndocumentation. Add an additional line to django-polls/MANIFEST.in:

    \n
    Text
    recursive-include docs *\n
    \n

    Note that the docs directory won’t be included in your package unless\nyou add some files to it. Many Django apps also provide their documentation\nonline through sites like readthedocs.org.

    \n
    9. \n

  9. Try building your package by running python setup.py sdist inside\ndjango-polls. This creates a directory called dist and builds your\nnew package, django-polls-0.1.tar.gz.

    10. \n
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For more information on packaging, see Python’s Tutorial on Packaging and\nDistributing Projects.

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Using your own packageLink to this heading#

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Since we moved the polls directory out of the project, it’s no longer\nworking. We’ll now fix this by installing our new django-polls package.

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    \n

  1. To install the package, use pip (you already installed it, right?):

    \n
    Shell
    python -m pip install --user django-polls/dist/django-polls-0.1.tar.gz\n
    \n
    2. \n

  2. Update mysite/settings.py to point to the new module name:

    \n
    Code
    INSTALLED_APPS = [\n    "django_polls.apps.PollsConfig",\n    ...,\n]\n
    \n
    3. \n

  3. Update mysite/urls.py to point to the new module name:

    \n
    Code
    urlpatterns = [\n    path("polls/", include("django_polls.urls")),\n    ...,\n]\n
    \n
    4. \n

  4. Run the development server to confirm the project continues to work.

    5. \n
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Publishing your appLink to this heading#

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Now that we’ve packaged and tested django-polls, it’s ready to share with\nthe world! If this wasn’t just an example, you could now:

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Installing Python packages with a virtual environmentLink to this heading#

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Earlier, we installed django-polls as a user library. This has some\ndisadvantages:

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Typically, these situations only arise once you’re maintaining several Django\nprojects. When they do, the best solution is to use venv. This tool allows you to maintain multiple isolated\nPython environments, each with its own copy of the libraries and package\nnamespace.

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