Creating Python packages

Introduction

Every package requires a setup.py file which describes the package.

Consider the following directory structure for a simple package:

+-- package_name
| |
+-- init.py
+-- setup.py

The init.py contains only the line def foo(): return 100.

The following setup.py will define the package:

from setuptools import setup
setup(
name='package_name', # package name
version='0.1', # version
description='Package Description', # short description
url='https://example.com', # package URL
install_requires=[], # list of packages this package depends
# on.
packages=['package_name'], # List of module names that installing
# this package will provide.
)

virtualenv is great to test package installs without modifying your other Python environments:

virtualenv .virtualenv
…
source .virtualenv/bin/activate
python setup.py install running install
…
Installed …/package_name-0.1-….egg
…
python

import package_name
package_name.foo() 100

Uploading to PyPI

Once your setup.py is fully functional (see Introduction), it is very easy to upload your package to PyPI.

Setup a .pypirc File

This file stores logins and passwords to authenticate your accounts. It is typically stored in your home directory.

.pypirc file

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[distutils]
index-servers =
pypi
pypitest
[pypi]
repository=https://pypi.python.org/pypi
username=your_username
password=your_password
[pypitest]
repository=https://testpypi.python.org/pypi
username=your_username
password=your_password

It is safer to use twine for uploading packages, so make sure that is installed.

$ pip install twine

Register and Upload to testpypi (optional)

Note: PyPI does not allow overwriting uploaded packages, so it is prudent to first test your deployment on a dedicated test server, e.g. testpypi. This option will be discussed. Consider a versioning scheme for your package prior to uploading such as calendar versioning or semantic versioning.

Either log in, or create a new account at testpypi. Registration is only required the first time, although registering more than once is not harmful.

$ python setup.py register -r pypitest

While in the root directory of your package:

$ twine upload dist/* -r pypitest

Your package should now be accessible through your account.

Testing

Make a test virtual environment. Try to pip install your package from either testpypi or PyPI.

Using virtualenv $ mkdir testenv
$ cd testenv
$ virtualenv .virtualenv
…
$ source .virtualenv/bin/activate
Test from testpypi
(.virtualenv) pip install --verbose --extra-index-url https://testpypi.python.org/pypi
package_name
…

Or test from PyPI

(.virtualenv) $ pip install package_name
…
(.virtualenv) $ python
Python 3.5.1 (default, Jan 27 2016, 19:16:39)
[GCC 4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import package_name

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package_name.foo()
100

If successful, your package is least importable. You might consider testing your API as well before your final upload to PyPI. If you package failed during testing, do not worry. You can still fix it, re-upload to testpypi and test again.

Register and Upload to PyPI

Make sure twine is installed:

$ pip install twine

Either log in, or create a new account at PyPI.

python setup.py register -r pypi
twine upload dist/*

That’s it! Your package is now live.

If you discover a bug, simply upload a new version of your package.

Documentation

Don’t forget to include at least some kind of documentation for your package. PyPi takes as the default formatting language reStructuredText.

Readme

If your package doesn’t have a big documentation, include what can help other users in README.rst file. When the file is ready, another one is needed to tell PyPi to show it.

Create setup.cfg file and put these two lines in it:

[metadata]
description-file = README.rst

Note that if you try to put Markdown file into your package, PyPi will read it as a pure text file without any formatting.

Licensing

It’s often more than welcome to put a LICENSE.txt file in your package with one of the OpenSource licenses to tell users if they can use your package for example in commercial projects or if your code is usable with their license.

In more readable way some licenses are explained at TL;DR.

Making package executable

If your package isn’t only a library, but has a piece of code that can be used either as a showcase or a standalone application when your package is installed, put that piece of code into main.py file.

Put the main.py in the package_name folder. This way you will be able to run it directly from console:

python -m package_name

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If there’s no main.py file available, the package won’t run with this command and this error will be printed:

python: No module named package_name.main; ‘package_name’ is a package and cannot be directly executed.

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