1.4. Module Distributing

1.4.1. Installing Packages

  • pip search

  • pip install

  • pip install -r requirements.txt

1.4.2. __init__.py

It is true that Python 3.3+ supports Implicit Namespace Packages that allows it to create a package without an __init__.py file. This is called a namespace package in contrast to a regular package which does have an __init__.py file (empty or not empty).

However, creating a namespace package should ONLY be done if there is a need for it. For most use cases and developers out there, this doesn't apply so you should stick with EMPTY __init__.py files regardless.

Namespace package use case

To demonstrate the difference between the two types of python packages, lets look at the following example:

google_pubsub/              <- Package 1
    google/                 <- Namespace package (there is no __init__.py)
        cloud/              <- Namespace package (there is no __init__.py)
            pubsub/         <- Regular package (with __init__.py)
                __init__.py <- Required to make the package a regular package

google_storage/             <- Package 2
    google/                 <- Namespace package (there is no __init__.py)
        cloud/              <- Namespace package (there is no __init__.py)
            storage/        <- Regular package (with __init__.py)
                __init__.py <- Required to make the package a regular package

google_pubsub and google_storage are separate packages but they share the same namespace google/cloud. In order to share the same namespace, it is required to make each directory of the common path a namespace package, i.e. google/ and cloud/. This should be the only use case for creating namespace packages, otherwise, there is no need for it.

It's crucial that there are no __init__py files in the google and google/cloud directories so that both directories can be interpreted as namespace packages. In Python 3.3+ any directory on the sys.path with a name that matches the package name being looked for will be recognized as contributing modules and subpackages to that package. As a result, when you import both from google_pubsub and google_storage, the Python interpreter will be able to find them.

This is different from regular packages which are self-contained meaning all parts live in the same directory hierarchy. When importing a package and the Python interpreter encounters a subdirectory on the sys.path with an __init__.py file, then it will create a single directory package containing only modules from that directory, rather than finding all appropriately named subdirectories outside that directory. This is perfectly fine for packages that don't want to share a namespace. I highly recommend taking a look at Traps for the Unwary in Python's Import System to get a better understanding of how Python importing behaves with regular and namespace package and what __init__.py traps to watch out for.


  • Only skip __init__.py files if you want to create namespace packages. Only create namespace packages if you have different libraries that reside in different locations and you want them each to contribute a subpackage to the parent package, i.e. the namespace package.

  • Keep on adding empty __init__py to your directories because 99% of the time you just want to create regular packages. Also, Python tools out there such as mypy and pytest require empty __init__.py files to interpret the code structure accordingly. This can lead to weird errors if not done with care.

1.4.3. __all__

from backend.api_v2.models.click import Click
from backend.api_v2.models.event import Event
from backend.api_v2.models.survey import Survey
from backend.api_v2.models.trial import Trial

__all__ = ['Click', 'Event', 'Survey', 'Trial']

1.4.4. Creating packages

1.4.5. TOML

requires = ["flit"]
build-backend = "flit.buildapi"

module = "fastapi"
author = "Sebastián Ramírez"
author-email = "tiangolo@gmail.com"
home-page = "https://github.com/tiangolo/fastapi"
classifiers = [
    "Intended Audience :: Information Technology",
    "Intended Audience :: System Administrators",
    "Operating System :: OS Independent",
    "Programming Language :: Python :: 3",
    "Programming Language :: Python",
    "Topic :: Internet",
    "Topic :: Software Development :: Libraries :: Application Frameworks",
    "Topic :: Software Development :: Libraries :: Python Modules",
    "Topic :: Software Development :: Libraries",
    "Topic :: Software Development",
    "Typing :: Typed",
    "Development Status :: 4 - Beta",
    "Environment :: Web Environment",
    "Framework :: AsyncIO",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3 :: Only",
    "Programming Language :: Python :: 3.6",
    "Programming Language :: Python :: 3.7",
    "Programming Language :: Python :: 3.8",
    "Topic :: Internet :: WWW/HTTP :: HTTP Servers",
    "Topic :: Internet :: WWW/HTTP",
requires = [
    "starlette ==0.14.2",
    "pydantic >=1.6.2,!=1.7,!=1.7.1,!=1.7.2,!=1.7.3,!=1.8,!=1.8.1,<2.0.0"
description-file = "README.md"
requires-python = ">=3.6"

Documentation = "https://fastapi.tiangolo.com/"

test = [
    "pytest ==5.4.3",
    "pytest-cov ==2.10.0",
    "pytest-asyncio >=0.14.0,<0.15.0",
    "mypy ==0.812",
    "flake8 >=3.8.3,<4.0.0",
    "black ==20.8b1",
    "isort >=5.0.6,<6.0.0",
    "requests >=2.24.0,<3.0.0",
    "httpx >=0.14.0,<0.15.0",
    "email_validator >=1.1.1,<2.0.0",
    "sqlalchemy >=1.3.18,<1.4.0",
    "peewee >=3.13.3,<4.0.0",
    "databases[sqlite] >=0.3.2,<0.4.0",
    "orjson >=3.2.1,<4.0.0",
    "ujson >=4.0.1,<5.0.0",
    "async_exit_stack >=1.0.1,<2.0.0",
    "async_generator >=1.10,<2.0.0",
    "python-multipart >=0.0.5,<0.0.6",
    "aiofiles >=0.5.0,<0.6.0",
    "flask >=1.1.2,<2.0.0"
doc = [
    "mkdocs >=1.1.2,<2.0.0",
    "mkdocs-material >=7.1.9,<8.0.0",
    "markdown-include >=0.6.0,<0.7.0",
    "mkdocs-markdownextradata-plugin >=0.1.7,<0.2.0",
    "typer-cli >=0.0.12,<0.0.13",
    "pyyaml >=5.3.1,<6.0.0"
dev = [
    "python-jose[cryptography] >=3.3.0,<4.0.0",
    "passlib[bcrypt] >=1.7.2,<2.0.0",
    "autoflake >=1.3.1,<2.0.0",
    "flake8 >=3.8.3,<4.0.0",
    "uvicorn[standard] >=0.12.0,<0.14.0",
    "graphene >=2.1.8,<3.0.0"
all = [
    "requests >=2.24.0,<3.0.0",
    "aiofiles >=0.5.0,<0.6.0",
    "jinja2 >=2.11.2,<3.0.0",
    "python-multipart >=0.0.5,<0.0.6",
    "itsdangerous >=1.1.0,<2.0.0",
    "pyyaml >=5.3.1,<6.0.0",
    "graphene >=2.1.8,<3.0.0",
    "ujson >=4.0.1,<5.0.0",
    "orjson >=3.2.1,<4.0.0",
    "email_validator >=1.1.1,<2.0.0",
    "uvicorn[standard] >=0.12.0,<0.14.0",
    "async_exit_stack >=1.0.1,<2.0.0",
    "async_generator >=1.10,<2.0.0"

profile = "black"
known_third_party = ["fastapi", "pydantic", "starlette"]

1.4.6. distutils

  • Provides support for building and installing additional modules into a Python.

  • The new modules may be either 100%-pure Python, or may be extension modules written in C, or may be collections of Python packages which include modules coded in both Python and C.

1.4.7. setuptools

  • Enhanced alternative to distutils that provides:

    1. support for declaring project dependencies

    2. additional mechanisms for configuring which files to include in source releases (including plugins for integration with version control systems)

    3. the ability to declare project "entry points", which can be used as the basis for application plugin systems

    4. the ability to automatically generate Windows command line executables at installation time rather than needing to prebuild them

    5. consistent behaviour across all supported Python versions

Setuptools is a fully-featured, actively-maintained, and stable library designed to facilitate packaging Python projects, where packaging includes:

  • Python package and module definitions

  • Distribution package metadata

  • Test hooks

  • Project installation

  • Platform-specific details

  • Python 3 support

1.4.8. wheel vs. egg

  • to build a python wheel package

  • sdist will generate a .tar.gz file in dist/

  • bdist_wheel will generate a .whl file in dist/

$ python setup.py sdist bdist_wheel
$ python setup.py sdist bdist_wheel --universal

1.4.9. requirements.txt vs setup.py

1.4.10. setup.py

from setuptools import find_packages
from setuptools import setup
from os import path

assert sys.version_info >= (3, 6), "Python 3.6+ required."

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

# Get the long description from the relevant file
with open(path.join(BASE_DIR, 'README.rst'), encoding='utf-8') as file:
    long_description = file.read()

# Get the project requirements from requirements.txt file
with open(path.join(BASE_DIR, 'requirements.txt'), encoding='utf-8') as file:
    requirements = file.read().splitlines()


    # Versions should comply with PEP440.  For a discussion on single-sourcing
    # the version across setup.py and the project code, see
    # https://packaging.python.org/en/latest/single_source_version.html

    description='Analog Habitat Operating System',

    # The project's main homepage.

    # Author details
    author='Matt Harasymczuk',

    # Choose your license

    # See https://pypi.python.org/pypi?:action=list_classifiers
        # How mature is this project? Common values are
        #   3 - Alpha
        #   4 - Beta
        #   5 - Production/Stable
        'Development Status :: 4 - Beta',

        # Indicate who your project is intended for
        'Intended Audience :: Science/Research',
        'Topic :: Scientific/Engineering',
        'Topic :: System :: Operating System',

        # Pick your license as you wish (should match "license" above)
        'License :: OSI Approved :: MIT License',

        # Specify the Python versions you support here. In particular, ensure
        # that you indicate whether you support Python 2, Python 3 or both.
        'Programming Language :: Python :: 3.6',

    # What does your project relate to?
    keywords='space exploration analog analogue habitat operating system',

    # You can just specify the packages manually here if your project is
    # simple. Or you can use find_packages().
    packages=find_packages(exclude=['contrib', 'docs', 'tests*']),

    # List run-time dependencies here.  These will be installed by pip when
    # your project is installed. For an analysis of "install_requires" vs pip's
    # requirements files see:
    # https://packaging.python.org/en/latest/requirements.html

    # List additional groups of dependencies here (e.g. development
    # dependencies). You can install these using the following syntax,
    # for example:
    # $ pip install -e .[dev,test]
        'dev': ['check-manifest'],
        'test': ['coverage', 'pep8'],

    # If there are data files included in your packages that need to be
    # installed, specify them here.  If using Python 2.6 or less, then these
    # have to be included in MANIFEST.in as well.
        # 'sample': ['package_data.dat'],

    # Although 'package_data' is the preferred approach, in some case you may
    # need to place data files outside of your packages. See:
    # http://docs.python.org/3.4/distutils/setupscript.html#installing-additional-files # noqa
    # In this case, 'data_file' will be installed into '<sys.prefix>/my_data'
    # data_files=[('my_data', ['data/data_file.txt'])],

    # To provide executable scripts, use entry points in preference to the
    # "scripts" keyword. Entry points provide cross-platform support and allow
    # pip to create the appropriate form of executable for the target platform.
        'console_scripts': [

1.4.11. setup.cfg

  • Configuring setup() using setup.cfg files

  • A setup.py file containing a setup() function call is still required even if your configuration resides in setup.cfg.

universal = 1

license_file = LICENSE

max-line-length = 999
exclude = */migrations/*
ignore = E402,W391
name = my_package
version = attr: src.VERSION
description = My package description
long_description = file: README.rst, CHANGELOG.rst, LICENSE.rst
keywords = one, two
license = BSD 3-Clause License
classifiers =
    Framework :: Django
    License :: OSI Approved :: BSD License
    Programming Language :: Python :: 3
    Programming Language :: Python :: 3.5

zip_safe = False
include_package_data = True
packages = find:
scripts =
install_requires =
  importlib; python_version == "2.6"

* = *.txt, *.rst
hello = *.msg

pdf = ReportLab>=1.2; RXP
rest = docutils>=0.3; pack ==1.1, ==1.3

exclude =

/etc/my_package =
data = data/img/logo.png, data/svg/icon.svg

1.4.12. python setup.py sdist upload

  • upload is deprecated in favor of using twine

1.4.13. twine

pip install twine
$ python setup.py sdist bdist_wheel

# Upload with twine to Test PyPI and verify things look right.
$ twine upload --repository-url https://test.pypi.org/legacy/ dist/*

# Upload to PyPI
$ twine upload dist/*

1.4.14. Signing packages

# Remove any old distributions
$ rm -rf dist/

# Create new tar.gz and wheel files
# Only create a universal wheel if py2/py3 compatible and no C extensions
$ python setup.py bdist_wheel --universal

# Sign the distributions
$ gpg --detach-sign -a dist/*

# Upload to PyPI
$ twine upload dist/*

1.4.15. Artifactory

$ docker run --name artifactory -d -p 8081:8081 docker.bintray.io/jfrog/artifactory-oss:latest


index-servers =

repository: https://pypi.org/pypi
username: myusername
password: mypassword

repository: http://localhost:8081/artifactory/api/pypi/pypi-local
username: myusername
password: mypassword
$ python setup.py sdist upload -r local
$ python setup.py bdist_wheel upload -r local
$ python setup.py sdist bdist_wheel upload -r local


$ pip search myapp --index http://localhost:8081/artifactory/api/pypi/pypi-local/
myapp                   - My Simple App

1.4.16. Further Reading