Building Your Own Package¶

The very basics of what you need to know to make your own package.

Why Build a Package?¶

There’s a bunch of tools that help you build, install and distribute packages.

Using a standard layout for your package makes it easy to use those tools.

Even if you never want to distribute your code, the standard layout eases development.

What is a Package?¶

A collection of modules

... and the documentation
... and the tests
... and any top-level scripts
... and any data files required
... and a way to build and install it...

Python packaging tools:¶

The distutils:

from distutils.core import setup

Getting klunky, hard to extend, maybe destined for deprication...

setuptools: extra features, wraps distutils, comes with “package manager” called easy_install

pip: for installing packages, a replacement for easy_install

wheel: for binary distributions

This packaging rant gives a lot of good background on the different Python packaging tools and evolution

setuptools¶

setuptools is an extension to distutils that provides a number of extensions:

from setuptools import setup

superset of the distutils setup

This buys you a bunch of additional functionality:

auto-finding packages

better script installation

resource (non-code files) management

develop mode

a LOT more

http://pythonhosted.org//setuptools/

PyPi¶

The Python package index:

https://pypi.python.org/pypi

You’ve all used this – pip install searches it.

To upload your package to PyPi:

python setup.py register

python setup.py sdist bdist_wheel upload

http://docs.python.org/2/distutils/packageindex.html

wheels¶

Wheels are a new binary format for packages.

http://wheel.readthedocs.org/en/latest/

Pretty simple, essentially an zip archive of all the stuff that gets put in

site-packages

Can be just pure python or binary with compiled extensions

Compatible with virtualenv.

Building a wheel:

python setup.py bdist_wheel

Create a set of wheels (a wheelhouse):

# Build a directory of wheels for pyramid and all its dependencies
pip wheel --wheel-dir=/tmp/wheelhouse pyramid

# Install from cached wheels
pip install --use-wheel --no-index --find-links=/tmp/wheelhouse pyramid

pip install packagename will find wheels for Windows and OS-X.

pip install --no-use-wheel avoids that.

Basic Package Structure:¶

package_name/
    bin/
    CHANGES.txt
    docs/
    LICENSE.txt
    MANIFEST.in
    README.txt
    setup.py
    package_name/
          __init__.py
          module1.py
          module2.py
          test/
              __init__.py
              test_module1.py
              test_module2.py

CHANGES.txt: log of changes with each release

LICENSE.txt: text of the license you choose (do choose one!)

MANIFEST.in: description of what non-code files to include

README.txt: description of the package – should be written in reST (for PyPi):

(http://docutils.sourceforge.net/rst.html)

setup.py: distutils script for building/installing package.

bin/: This is where you put top-level scripts

( some folks use scripts )

docs/: the documentation

package_name/: The main pacakge – this is where the code goes.

test/: your unit tests. Options here:

Put it inside the package – supports

$ pip install package_name
>> import package_name.test
>> package_name.test.runall()

Or keep it at the top level.

The `setup.py` File¶

Your setup.py file is what describes your package, and tells the distutils how to pacakge, build and install it

It is python code, so you can add anything custom you need to it

But in the simple case, it is essentially declarative.

http://docs.python.org/2/distutils/

 from setuptools import setup

 setup(
   name='PackageName',
   version='0.1.0',
   author='An Awesome Coder',
   author_email='aac@example.com',
   packages=['package_name', 'package_name.test'],
   scripts=['bin/script1','bin/script2'],
   url='http://pypi.python.org/pypi/PackageName/',
   license='LICENSE.txt',
   description='An awesome package that does something',
   long_description=open('README.txt').read(),
   install_requires=[
       "Django >= 1.1.1",
       "pytest",
   ],
)

`setup.cfg`¶

setup.cfg provides a way to give the end user some ability to customise the install

It’s an ini style file:

[command]
option=value
...

simple to read and write.

command is one of the Distutils commands (e.g. build_py, install)

option is one of the options that command supports.

Note that an option spelled --foo-bar on the command-line is spelled f``foo_bar`` in configuration files.

Where do I go to figure this out?¶

This is a really good guide:

Python Packaging User Guide:

https://packaging.python.org/en/latest/

Follow it!

And a sample project here:

https://github.com/pypa/sampleproject

(this has all the complexity you might need...)

Running `setup.py` ( build, install, develop )¶

With a setup.py script defined you can do a lot:

build from source:
```
python setup.py build
```
and install:
```
python setup.py install
```

and develop:

python setup.py develop
# uninstall like this, or you might run into a gotcha
python setup.py develop --uninstall

What did each of these steps really do? How can we inspect the outcomes?

Under Development¶

Develop mode is really really nice:

python setup.py develop

It puts links into the python installation to your code, so that your package is installed, but any changes will immediately take effect.

This way all your test code, and client code, etc, can all import your package the usual way.

No sys.path hacking

Good idea to use it for anything more than a single file project.

(requires setuptools)

Running `setup.py` ( source and binary distros )¶

With a setup.py script you can also create your distribution packages:

builds a source distribution (defaults to tar file):

python setup.py sdist
python setup.py sdist --format=zip

builds binary distributions:

python setup.py bdist_rpm
python setup.py bdist_wininst

(other, more obscure ones, too....)

But you probably want to use wheel for binary disributions now.

Getting Started Hints¶

For anything but a single-file script (and maybe even then):

Create the basic package structure
Write a setup.py
python setup.py develop
Put some tests in package/test
py.test or nosetests

LAB¶

Create a small package
- package structure
- setup.py
- python setup.py develop
If you are ready – it can be the start of your project package.

(example in code/Capitalize)