6. Examples
***********

This chapter provides a number of basic examples to help get started
with distutils.  Additional information about using distutils can be
found in the Distutils Cookbook.

See also:

  Distutils Cookbook
     Collection of recipes showing how to achieve more control over
     distutils.


6.1. Pure Python distribution (by module)
=========================================

If you’re just distributing a couple of modules, especially if they
don’t live in a particular package, you can specify them individually
using the "py_modules" option in the setup script.

In the simplest case, you’ll have two files to worry about: a setup
script and the single module you’re distributing, "foo.py" in this
example:

   <root>/
           setup.py
           foo.py

(In all diagrams in this section, *<root>* will refer to the
distribution root directory.)  A minimal setup script to describe this
situation would be:

   from distutils.core import setup
   setup(name='foo',
         version='1.0',
         py_modules=['foo'],
         )

Note that the name of the distribution is specified independently with
the "name" option, and there’s no rule that says it has to be the same
as the name of the sole module in the distribution (although that’s
probably a good convention to follow).  However, the distribution name
is used to generate filenames, so you should stick to letters, digits,
underscores, and hyphens.

Since "py_modules" is a list, you can of course specify multiple
modules, eg. if you’re distributing modules "foo" and "bar", your
setup might look like this:

   <root>/
           setup.py
           foo.py
           bar.py

and the setup script might be

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         py_modules=['foo', 'bar'],
         )

You can put module source files into another directory, but if you
have enough modules to do that, it’s probably easier to specify
modules by package rather than listing them individually.


6.2. Pure Python distribution (by package)
==========================================

If you have more than a couple of modules to distribute, especially if
they are in multiple packages, it’s probably easier to specify whole
packages rather than individual modules.  This works even if your
modules are not in a package; you can just tell the Distutils to
process modules from the root package, and that works the same as any
other package (except that you don’t have to have an "__init__.py"
file).

The setup script from the last example could also be written as

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         packages=[''],
         )

(The empty string stands for the root package.)

If those two files are moved into a subdirectory, but remain in the
root package, e.g.:

   <root>/
           setup.py
           src/      foo.py
                     bar.py

then you would still specify the root package, but you have to tell
the Distutils where source files in the root package live:

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         package_dir={'': 'src'},
         packages=[''],
         )

More typically, though, you will want to distribute multiple modules
in the same package (or in sub-packages).  For example, if the "foo"
and "bar" modules belong in package "foobar", one way to layout your
source tree is

   <root>/
           setup.py
           foobar/
                    __init__.py
                    foo.py
                    bar.py

This is in fact the default layout expected by the Distutils, and the
one that requires the least work to describe in your setup script:

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         packages=['foobar'],
         )

If you want to put modules in directories not named for their package,
then you need to use the "package_dir" option again.  For example, if
the "src" directory holds modules in the "foobar" package:

   <root>/
           setup.py
           src/
                    __init__.py
                    foo.py
                    bar.py

an appropriate setup script would be

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         package_dir={'foobar': 'src'},
         packages=['foobar'],
         )

Or, you might put modules from your main package right in the
distribution root:

   <root>/
           setup.py
           __init__.py
           foo.py
           bar.py

in which case your setup script would be

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         package_dir={'foobar': ''},
         packages=['foobar'],
         )

(The empty string also stands for the current directory.)

If you have sub-packages, they must be explicitly listed in
"packages", but any entries in "package_dir" automatically extend to
sub-packages. (In other words, the Distutils does *not* scan your
source tree, trying to figure out which directories correspond to
Python packages by looking for "__init__.py" files.)  Thus, if the
default layout grows a sub-package:

   <root>/
           setup.py
           foobar/
                    __init__.py
                    foo.py
                    bar.py
                    subfoo/
                              __init__.py
                              blah.py

then the corresponding setup script would be

   from distutils.core import setup
   setup(name='foobar',
         version='1.0',
         packages=['foobar', 'foobar.subfoo'],
         )


6.3. Single extension module
============================

Extension modules are specified using the "ext_modules" option.
"package_dir" has no effect on where extension source files are found;
it only affects the source for pure Python modules.  The simplest
case, a single extension module in a single C source file, is:

   <root>/
           setup.py
           foo.c

If the "foo" extension belongs in the root package, the setup script
for this could be

   from distutils.core import setup
   from distutils.extension import Extension
   setup(name='foobar',
         version='1.0',
         ext_modules=[Extension('foo', ['foo.c'])],
         )

If the extension actually belongs in a package, say "foopkg", then

With exactly the same source tree layout, this extension can be put in
the "foopkg" package simply by changing the name of the extension:

   from distutils.core import setup
   from distutils.extension import Extension
   setup(name='foobar',
         version='1.0',
         ext_modules=[Extension('foopkg.foo', ['foo.c'])],
         )


6.4. Checking a package
=======================

The "check" command allows you to verify if your package meta-data
meet the minimum requirements to build a distribution.

To run it, just call it using your "setup.py" script. If something is
missing, "check" will display a warning.

Let’s take an example with a simple script:

   from distutils.core import setup

   setup(name='foobar')

Running the "check" command will display some warnings:

   $ python setup.py check
   running check
   warning: check: missing required meta-data: version, url
   warning: check: missing meta-data: either (author and author_email) or
            (maintainer and maintainer_email) must be supplied

If you use the reStructuredText syntax in the "long_description" field
and docutils  is installed you can check if the syntax is fine with
the "check" command, using the "restructuredtext" option.

For example, if the "setup.py" script is changed like this:

   from distutils.core import setup

   desc = """\
   My description
   ==============

   This is the description of the ``foobar`` package.
   """

   setup(name='foobar', version='1', author='tarek',
       author_email='tarek@ziade.org',
       url='http://example.com', long_description=desc)

Where the long description is broken, "check" will be able to detect
it by using the "docutils" parser:

   $ python setup.py check --restructuredtext
   running check
   warning: check: Title underline too short. (line 2)
   warning: check: Could not finish the parsing.


6.5. Reading the metadata
=========================

The "distutils.core.setup()" function provides a command-line
interface that allows you to query the metadata fields of a project
through the "setup.py" script of a given project:

   $ python setup.py --name
   distribute

This call reads the "name" metadata by running the
"distutils.core.setup()"  function. Although, when a source or binary
distribution is created with Distutils, the metadata fields are
written in a static file called "PKG-INFO". When a Distutils-based
project is installed in Python, the "PKG-INFO" file is copied
alongside the modules and packages of the distribution under "NAME-
VERSION-pyX.X.egg-info", where "NAME" is the name of the project,
"VERSION" its version as defined in the Metadata, and "pyX.X" the
major and minor version of Python like "2.7" or "3.2".

You can read back this static file, by using the
"distutils.dist.DistributionMetadata" class and its "read_pkg_file()"
method:

   >>> from distutils.dist import DistributionMetadata
   >>> metadata = DistributionMetadata()
   >>> metadata.read_pkg_file(open('distribute-0.6.8-py2.7.egg-info'))
   >>> metadata.name
   'distribute'
   >>> metadata.version
   '0.6.8'
   >>> metadata.description
   'Easily download, build, install, upgrade, and uninstall Python packages'

Notice that the class can also be instantiated with a metadata file
path to loads its values:

   >>> pkg_info_path = 'distribute-0.6.8-py2.7.egg-info'
   >>> DistributionMetadata(pkg_info_path).name
   'distribute'
