Python setuptools

The most common way to distribute Python modules is using PyPI, the Python Package Index (formerly known as the Cheese shop).

The tool to download and install packages is pip. Predecessors like EasyInstall are no longer recommended, with only a few exceptions (in particular pip does not support binary distributions).

There are tool to build and upload packages is or setuptools. Make sure to use version 0.7 or later.

There are a few alternatives to setuptools: distutils is a tool in the standard library with limited functionality. The downside of both distutils and setuptools is that they use a script rather than a file format to store metadata, and force the developer an end-user to use the same tool to build and install the software. distutils2 (the module will be named `package`) is an attempt to move to a modern packaging system for Python, but has not been included as of Python 3.4.

Release Steps
Credit: These steps are based on the sphinxcontrib-aafig documentation.

In order to make a PyPi release, do the following steps:


 * 1) Make sure the repository is up-to date.
 * 2) Ensure the version is incremented:
 * 3) *  must be updated
 * 4) *  must be updated
 * 5) *  must contain a summary of the changes
 * 6) Make sure all changes are committed, including the version number changes.
 * 7) Tag the sources with   or.
 * 8) Push the code and tag:   or
 * 9) Temporarily modify   file to comment out the variables   and   (do not commit this change).
 * 10) Register and upload the new release.
 * 11) Generate the documentation with.
 * 12) Upload the new documentation (to PyPi or to github mypackage.wiki repository).

Package and Egg Loading Trickery
Python has a rather poor system of loading modules. Tools such as setuptools work around this problem, but sometimes these workarounds have unintended consequences.


 * Problem: always loaded this package from site-packages directory, despite that the   module was also available in the current directory, and   contained the current directory as first entry.
 * Cause:easy-install 'only' modifies  (overriding  ). setuptools takes it a step further and creates a   file that manipulates.
 * Solution: if it exists.

First of all: Python eggs are a neat way to distribute different software packages inside the same Python package. Consider the following two directory structures:

site-packages/ sphinxcontrib/ blockdiag/ restbuilder/ swf/

and

site-packages/ sphinxcontrib-blockdiag-1.2.egg sphinxcontrib/ blockdiag/ sphinxcontrib-restbuilder-0.1.egg sphinxcontrib/ restbuilder/ sphinxcontrib-swf-0.3.egg sphinxcontrib/ swf/

The second directory structure allows separate release cycles for all three packages. The downside is that all  directories need to be included in. However, this leads to problems when a user tries to. Which of these directories should be included? setuptools accommodates for this by adding scripts in  files that select the correct packages. This is even the case if the directory structure is merged, as it is in the first example directory structure above.

To be exact, setuptools adds an empty module to  with just the name and the desired path of each module inside an egg folder. As a consequence, as soon as that module is loaded,  is not used, and that directory specified in   is used.

Here is the  file installed by setuptools. It is slightly rewritten for clarity.

import sys, types, os p = os.path.join(sys._getframe(1).f_locals['sitedir'], 'sphinxcontrib') if os.path.exists(os.path.join(p,'__init__.py')): mp = [] else: m = sys.modules.setdefault('sphinxcontrib', types.ModuleType('sphinxcontrib')) mp = m.__dict__.setdefault('__path__',[]) if (p not in mp): mp.append(p)

In case a script must use another version of the module, manipulating  won't help. Instead, take one of these steps: 1. Delete the  file beforehand. (This may give problems when normally loading the module if it is in an egg file) 2. Delete the entry in  for the given module: , and manipulate   as usual. 3. Replace the entry in  with one pointing to another path:

Further reading:
 * Python Packaging: Hate, hate, hate everywhere by Armin Ronacher gives some background on the different tools (easy-install, setuptools, and pip).
 * Python site module, which is responsible for defining, and executing the   files during Python boot time.