Packaging Python Projects

This tutorial walks you through how to package a simple Python project. It will show you how to add the necessary files and structure to create the package, how to build the package, and how to upload it to the Python Package Index.

Tip

If you have trouble running the commands in this tutorial, please copy the command and its output, then open an issue on the packaging-problems repository on GitHub. We’ll do our best to help you!

Some of the commands require a newer version of pip, so start by making sure you have the latest version installed:

python3 -m pip install --upgrade pip

py -m pip install --upgrade pip

A simple project

This tutorial uses a simple project named example_package. We recommend following this tutorial as-is using this project, before packaging your own project.

Create the following file structure locally:

packaging_tutorial/
└── src/
    └── example_package/
        ├── __init__.py
        └── example.py

__init__.py is required to import the directory as a package, and should be empty.

example.py is an example of a module within the package that could contain the logic (functions, classes, constants, etc.) of your package. Open that file and enter the following content:

def add_one(number):
    return number + 1

If you are unfamiliar with Python’s modules and import packages, take a few minutes to read over the Python documentation for packages and modules.

Once you create this structure, you’ll want to run all of the commands in this tutorial within the packaging_tutorial directory.

Creating the package files

You will now add files that are used to prepare the project for distribution. When you’re done, the project structure will look like this:

packaging_tutorial/
├── LICENSE
├── pyproject.toml
├── README.md
├── setup.cfg
├── src/
│   └── example_package/
│       ├── __init__.py
│       └── example.py
└── tests/

Creating a test directory

tests/ is a placeholder for test files. Leave it empty for now.

Creating pyproject.toml

pyproject.toml tells build tools (like pip and build) what is required to build your project. This tutorial uses setuptools, so open pyproject.toml and enter the following content:

[build-system]
requires = [
    "setuptools>=42",
    "wheel"
]
build-backend = "setuptools.build_meta"

build-system.requires gives a list of packages that are needed to build your package. Listing something here will only make it available during the build, not after it is installed.

build-system.build-backend is the name of Python object that will be used to perform the build. If you were to use a different build system, such as flit or poetry, those would go here, and the configuration details would be completely different than the setuptools configuration described below.

See PEP 517 and PEP 518 for background and details.

Configuring metadata

There are two types of metadata: static and dynamic.

  • Static metadata (setup.cfg): guaranteed to be the same every time. This is simpler, easier to read, and avoids many common errors, like encoding errors.

  • Dynamic metadata (setup.py): possibly non-deterministic. Any items that are dynamic or determined at install-time, as well as extension modules or extensions to setuptools, need to go into setup.py.

Static metadata (setup.cfg) should be preferred. Dynamic metadata (setup.py) should be used only as an escape hatch when absolutely necessary. setup.py used to be required, but can be omitted with newer versions of setuptools and pip.

setup.cfg is the configuration file for setuptools. It tells setuptools about your package (such as the name and version) as well as which code files to include. Eventually much of this configuration may be able to move to pyproject.toml.

Open setup.cfg and enter the following content. Change the name to include your username; this ensures that you have a unique package name and that your package doesn’t conflict with packages uploaded by other people following this tutorial.

[metadata]
name = example-package-YOUR-USERNAME-HERE
version = 0.0.1
author = Example Author
author_email = author@example.com
description = A small example package
long_description = file: README.md
long_description_content_type = text/markdown
url = https://github.com/pypa/sampleproject
project_urls =
    Bug Tracker = https://github.com/pypa/sampleproject/issues
classifiers =
    Programming Language :: Python :: 3
    License :: OSI Approved :: MIT License
    Operating System :: OS Independent

[options]
package_dir =
    = src
packages = find:
python_requires = >=3.6

[options.packages.find]
where = src

There are a variety of metadata and options supported here. This is in configparser format; do not place quotes around values. This example package uses a relatively minimal set of metadata:

  • name is the distribution name of your package. This can be any name as long as it only contains letters, numbers, _ , and -. It also must not already be taken on pypi.org. Be sure to update this with your username, as this ensures you won’t try to upload a package with the same name as one which already exists.

  • version is the package version. See PEP 440 for more details on versions. You can use file: or attr: directives to read from a file or package attribute.

  • author and author_email are used to identify the author of the package.

  • description is a short, one-sentence summary of the package.

  • long_description is a detailed description of the package. This is shown on the package detail page on the Python Package Index. In this case, the long description is loaded from README.md (which is a common pattern) using the file: directive.

  • long_description_content_type tells the index what type of markup is used for the long description. In this case, it’s Markdown.

  • url is the URL for the homepage of the project. For many projects, this will just be a link to GitHub, GitLab, Bitbucket, or similar code hosting service.

  • project_urls lets you list any number of extra links to show on PyPI. Generally this could be to documentation, issue trackers, etc.

  • classifiers gives the index and pip some additional metadata about your package. In this case, the package is only compatible with Python 3, is licensed under the MIT license, and is OS-independent. You should always include at least which version(s) of Python your package works on, which license your package is available under, and which operating systems your package will work on. For a complete list of classifiers, see https://pypi.org/classifiers/.

In the options category, we have controls for setuptools itself:

  • package_dir is a mapping of package names and directories. An empty package name represents the “root package” — the directory in the project that contains all Python source files for the package — so in this case the src directory is designated the root package.

  • packages is a list of all Python import packages that should be included in the distribution package. Instead of listing each package manually, we can use the find: directive to automatically discover all packages and subpackages and options.packages.find to specify the package_dir to use. In this case, the list of packages will be example_package as that’s the only package present.

  • python_requires gives the versions of Python supported by your project. Installers like pip will look back through older versions of packages until it finds one that has a matching Python version.

There are many more than the ones mentioned here. See Packaging and distributing projects for more details.

setup.py is the build script for setuptools. It tells setuptools about your package (such as the name and version) as well as which code files to include.

Open setup.py and enter the following content. Change the name to include your username; this ensures that you have a unique package name and that your package doesn’t conflict with packages uploaded by other people following this tutorial.

import setuptools

with open("README.md", "r", encoding="utf-8") as fh:
    long_description = fh.read()

setuptools.setup(
    name="example-package-YOUR-USERNAME-HERE",
    version="0.0.1",
    author="Example Author",
    author_email="author@example.com",
    description="A small example package",
    long_description=long_description,
    long_description_content_type="text/markdown",
    url="https://github.com/pypa/sampleproject",
    project_urls={
        "Bug Tracker": "https://github.com/pypa/sampleproject/issues",
    },
    classifiers=[
        "Programming Language :: Python :: 3",
        "License :: OSI Approved :: MIT License",
        "Operating System :: OS Independent",
    ],
    package_dir={"": "src"},
    packages=setuptools.find_packages(where="src"),
    python_requires=">=3.6",
)

setup() takes several arguments. This example package uses a relatively minimal set:

  • name is the distribution name of your package. This can be any name as long as it only contains letters, numbers, _ , and -. It also must not already be taken on pypi.org. Be sure to update this with your username, as this ensures you won’t try to upload a package with the same name as one which already exists.

  • version is the package version. See PEP 440 for more details on versions.

  • author and author_email are used to identify the author of the package.

  • description is a short, one-sentence summary of the package.

  • long_description is a detailed description of the package. This is shown on the package detail page on the Python Package Index. In this case, the long description is loaded from README.md, which is a common pattern.

  • long_description_content_type tells the index what type of markup is used for the long description. In this case, it’s Markdown.

  • url is the URL for the homepage of the project. For many projects, this will just be a link to GitHub, GitLab, Bitbucket, or similar code hosting service.

  • project_urls lets you list any number of extra links to show on PyPI. Generally this could be to documentation, issue trackers, etc.

  • classifiers gives the index and pip some additional metadata about your package. In this case, the package is only compatible with Python 3, is licensed under the MIT license, and is OS-independent. You should always include at least which version(s) of Python your package works on, which license your package is available under, and which operating systems your package will work on. For a complete list of classifiers, see https://pypi.org/classifiers/.

  • package_dir is a dictionary with package names for keys and directories for values. An empty package name represents the “root package” — the directory in the project that contains all Python source files for the package — so in this case the src directory is designated the root package.

  • packages is a list of all Python import packages that should be included in the distribution package. Instead of listing each package manually, we can use find_packages() to automatically discover all packages and subpackages under package_dir. In this case, the list of packages will be example_package as that’s the only package present.

  • python_requires gives the versions of Python supported by your project. Installers like pip will look back though older versions of packages until it finds one that has a matching Python version.

There are many more than the ones mentioned here. See Packaging and distributing projects for more details.

Warning

You may see some existing projects or other Python packaging tutorials that import their setup function from distutils.core rather than setuptools. This is a legacy approach that installers support for backwards compatibility purposes 1, but using the legacy distutils API directly in new projects is strongly discouraged, since distutils is deprecated as per PEP 632 and will be removed from the standard library in Python 3.12.

Creating README.md

Open README.md and enter the following content. You can customize this if you’d like.

# Example Package

This is a simple example package. You can use
[Github-flavored Markdown](https://guides.github.com/features/mastering-markdown/)
to write your content.

Because our configuration loads README.md to provide a long_description, README.md must be included along with your code when you generate a source distribution. Newer versions of setuptools will do this automatically.

Creating a LICENSE

It’s important for every package uploaded to the Python Package Index to include a license. This tells users who install your package the terms under which they can use your package. For help picking a license, see https://choosealicense.com/. Once you have chosen a license, open LICENSE and enter the license text. For example, if you had chosen the MIT license:

Copyright (c) 2018 The Python Packaging Authority

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Including other files

The files listed above will be included automatically in your source distribution. If you want to control what goes in this explicitly, see Including files in source distributions with MANIFEST.in.

The final built distribution will have the Python files in the discovered or listed Python packages. If you want to control what goes here, such as to add data files, see Including Data Files from the setuptools docs.

Generating distribution archives

The next step is to generate distribution packages for the package. These are archives that are uploaded to the Python Package Index and can be installed by pip.

Make sure you have the latest version of PyPA’s build installed:

python3 -m pip install --upgrade build

py -m pip install --upgrade build

Tip

If you have trouble installing these, see the Installing Packages tutorial.

Now run this command from the same directory where pyproject.toml is located:

python3 -m build

py -m build

This command should output a lot of text and once completed should generate two files in the dist directory:

dist/
  example-package-YOUR-USERNAME-HERE-0.0.1-py3-none-any.whl
  example-package-YOUR-USERNAME-HERE-0.0.1.tar.gz

The tar.gz file is a source archive whereas the .whl file is a built distribution. Newer pip versions preferentially install built distributions, but will fall back to source archives if needed. You should always upload a source archive and provide built archives for the platforms your project is compatible with. In this case, our example package is compatible with Python on any platform so only one built distribution is needed.

Uploading the distribution archives

Finally, it’s time to upload your package to the Python Package Index!

The first thing you’ll need to do is register an account on TestPyPI, which is a separate instance of the package index intended for testing and experimentation. It’s great for things like this tutorial where we don’t necessarily want to upload to the real index. To register an account, go to https://test.pypi.org/account/register/ and complete the steps on that page. You will also need to verify your email address before you’re able to upload any packages. For more details, see Using TestPyPI.

To securely upload your project, you’ll need a PyPI API token. Create one at https://test.pypi.org/manage/account/#api-tokens, setting the “Scope” to “Entire account”. Don’t close the page until you have copied and saved the token — you won’t see that token again.

Now that you are registered, you can use twine to upload the distribution packages. You’ll need to install Twine:

python3 -m pip install --upgrade twine

py -m pip install --upgrade twine

Once installed, run Twine to upload all of the archives under dist:

python3 -m twine upload --repository testpypi dist/*

py -m twine upload --repository testpypi dist/*

You will be prompted for a username and password. For the username, use __token__. For the password, use the token value, including the pypi- prefix.

After the command completes, you should see output similar to this:

Uploading distributions to https://test.pypi.org/legacy/
Enter your username: [your username]
Enter your password:
Uploading example-package-YOUR-USERNAME-HERE-0.0.1-py3-none-any.whl
100%|█████████████████████| 4.65k/4.65k [00:01<00:00, 2.88kB/s]
Uploading example-package-YOUR-USERNAME-HERE-0.0.1.tar.gz
100%|█████████████████████| 4.25k/4.25k [00:01<00:00, 3.05kB/s]

Once uploaded your package should be viewable on TestPyPI, for example, https://test.pypi.org/project/example-package-YOUR-USERNAME-HERE

Installing your newly uploaded package

You can use pip to install your package and verify that it works. Create a virtual environment and install your package from TestPyPI:

python3 -m pip install --index-url https://test.pypi.org/simple/ --no-deps example-package-YOUR-USERNAME-HERE

py -m pip install --index-url https://test.pypi.org/simple/ --no-deps example-package-YOUR-USERNAME-HERE

Make sure to specify your username in the package name!

pip should install the package from TestPyPI and the output should look something like this:

Collecting example-package-YOUR-USERNAME-HERE
  Downloading https://test-files.pythonhosted.org/packages/.../example-package-YOUR-USERNAME-HERE-0.0.1-py3-none-any.whl
Installing collected packages: example-package-YOUR-USERNAME-HERE
Successfully installed example-package-YOUR-USERNAME-HERE-0.0.1

Note

This example uses --index-url flag to specify TestPyPI instead of live PyPI. Additionally, it specifies --no-deps. Since TestPyPI doesn’t have the same packages as the live PyPI, it’s possible that attempting to install dependencies may fail or install something unexpected. While our example package doesn’t have any dependencies, it’s a good practice to avoid installing dependencies when using TestPyPI.

You can test that it was installed correctly by importing the package. Make sure you’re still in your virtual environment, then run Python:

python3

py

and import the package:

>>> from example_package import example
>>> example.add_one(2)
3

Note that the import package is example_package regardless of what name you gave your distribution package in setup.cfg or setup.py (in this case, example-package-YOUR-USERNAME-HERE).

Next steps

Congratulations, you’ve packaged and distributed a Python project! ✨ 🍰 ✨

Keep in mind that this tutorial showed you how to upload your package to Test PyPI, which isn’t a permanent storage. The Test system occasionally deletes packages and accounts. It is best to use TestPyPI for testing and experiments like this tutorial.

When you are ready to upload a real package to the Python Package Index you can do much the same as you did in this tutorial, but with these important differences:

  • Choose a memorable and unique name for your package. You don’t have to append your username as you did in the tutorial.

  • Register an account on https://pypi.org - note that these are two separate servers and the login details from the test server are not shared with the main server.

  • Use twine upload dist/* to upload your package and enter your credentials for the account you registered on the real PyPI. Now that you’re uploading the package in production, you don’t need to specify --repository; the package will upload to https://pypi.org/ by default.

  • Install your package from the real PyPI using python3 -m pip install [your-package].

At this point if you want to read more on packaging Python libraries here are some things you can do:

1

Some legacy Python environments may not have setuptools pre-installed, and the operators of those environments may still be requiring users to install packages by running setup.py install commands, rather than providing an installer like pip that automatically installs required build dependendencies. These environments will not be able to use many published packages until the environment is updated to provide an up to date Python package installation client (e.g. by running python -m ensurepip).