Close #19407: New installation & distribution guides

- based on pip and other PyPA tools
- includes references to the new Python Packaging User Guide
  where appropriate (and the relevant section is at least
  partially filled in)
- started new FAQ sections
- both guides aim to introduce users to basic open source
  concepts if they aren't aware of them
- existing guides have been relocated (now linked from the
  distutils docs) rather then removed, since there is
  some needed material that has yet to be relocated to the
  distutils docs as a reference for the legacy formats

Doc/installing/index.rst

@@ -0,0 +1,211 @@
+.. highlightlang:: none
+
+.. _installing-index:
+
+*****************************
+  Installing Python Modules
+*****************************
+
+:Email: distutils-sig@python.org
+
+As a popular open source development project, Python has an active
+supporting community of contributors and users that also make their software
+available for other Python developers to use under open source license terms.
+
+This allows Python users to share and collaborate effectively, benefiting
+from the solutions others have already created to common (and sometimes
+even rare!) problems, as well as potentially contributing their own
+solutions to the common pool.
+
+This guide covers the installation part of the process. For a guide to
+creating and sharing your own Python projects, refer to the
+:ref:`distribution guide <distributing-index>`.
+
+.. note::
+
+   For corporate and other institutional users, be aware that many
+   organisations have their own policies around using and contributing to
+   open source software. Please take such policies into account when making
+   use of the distribution and installation tools provided with Python.
+
+
+Key terms
+=========
+
+* ``pip`` is the preferred installer program. Starting with Python 3.4, it
+  is included by default with the Python binary installers.
+  installed into virtual environments
+* a virtual environment is a semi-isolated Python environment that allows
+  packages to be installed for use by a particular application, rather than
+  being installed system wide
+* ``pyvenv`` is the standard tool for creating virtual environments, and has
+  been part of Python since Python 3.3. Starting with Python 3.4, it
+  defaults to installing ``pip`` into all created virtual environments
+* the `Python Package Index <https://pypi.python.org/pypi>`__ is a public
+  repository of open source licensed packages made available for use by
+  other Python users
+* the `Python Packaging Authority
+  <http://packaging.python.org/en/latest/future.html>`__ are the group of
+  developers and documentation authors responsible for the maintenance and
+  evolution of the standard packaging tools and the associated metadata and
+  file format standards. They maintain a variety of tools, documentation
+  and issue trackers on both `GitHub <https://github.com/pypa>` and
+  `BitBucket <https://bitbucket.org/pypa/>`__.
+* ``distutils`` is the original build and distribution system first added to
+  the Python standard library in 1998. While direct use of ``distutils`` is
+  being phased out, it still laid the foundation for the current packaging
+  and distribution infrastructure, and it not only remains part of the
+  standard library, but its name lives on in other ways (such as the name
+  of the mailing list used to coordinate Python packaging standards
+  development).
+
+
+Basic usage
+===========
+
+The standard packaging tools are all designed to be used from the command
+line. For Windows users, the examples below assume that the option to
+adjust the system PATH environment variable was selected when installing
+Python. For Linux users, the command to install into the system version of
+Python 3 is likely to be ``pip3`` rather than ``pip``.
+
+The following command will install the latest version of a module and its
+dependencies from the Python Package Index::
+
+    pip install SomePackage
+
+It's also possible to specify an exact or minimum version directly on the
+command line::
+
+    pip install SomePackage==1.0.4    # specific version
+    pip install 'SomePackage>=1.0.4'  # minimum version
+
+Normally, if a suitable module is already installed, attempting to install
+it again will have no effect. Upgrading existing modules must be requested
+explicitly::
+
+    pip install --upgrade SomePackage
+
+More information and resources regarding ``pip`` and its capabilities can be
+found in the `Python Packaging User Guide <http://packaging.python.org>`__.
+
+``pyvenv`` has its own documentation at :ref:`scripts-pyvenv`. Installing
+into an active virtual environment uses the commands shown above.
+
+.. seealso::
+
+    `Python Packaging User Guide: Installing Python packages
+    <http://packaging.python.org/en/latest/tutorial.html#installing-python-packages>`__
+
+
+How do I ...?
+=============
+
+These are quick answers or links for some common tasks.
+
+... install ``pip`` in versions of Python prior to Python 3.4?
+--------------------------------------------------------------
+
+Python only started bundling ``pip`` with Python 3.4. For earlier versions,
+``pip`` needs to be "bootstrapped" as described in the Python Packaging
+User Guide.
+
+.. seealso::
+
+   `Python Packaging User Guide: Installing the Tools
+   <http://packaging.python.org/en/latest/tutorial.html#installing-the-tools>`__
+
+
+.. installing-per-user-installation:
+
+... install packages just for the current user?
+-----------------------------------------------
+
+Passing the ``--user`` option to ``pip install`` will install a package
+just for the current user, rather than for all users of the system.
+
+
+... install scientific Python packages?
+---------------------------------------
+
+A number of scientific Python packages have complex binary dependencies, and
+aren't currently easy to install using ``pip`` directly. At this point in
+time, it will often be easier for users to install these packages by
+`other means
+<http://packaging.python.org/en/latest/platforms.html#installing-scientific-packages>`__
+rather than attempting to install them with ``pip``.
+
+.. seealso::
+
+   `Python Packaging User Guide: Installing Scientific Packages
+   <http://packaging.python.org/en/latest/platforms.html#installing-scientific-packages>`__
+
+
+... work with multiple versions of Python installed in parallel?
+----------------------------------------------------------------
+
+On Linux, Mac OS X and other POSIX systems, use the versioned Python commands
+in combination with the ``-m`` switch to run the appropriate copy of
+``pip``::
+
+   python2   -m pip install SomePackage  # default Python 2
+   python2.7 -m pip install SomePackage  # specifically Python 2.7
+   python3   -m pip install SomePackage  # default Python 3
+   python3.4 -m pip install SomePackage  # specifically Python 3.4
+
+(appropriately versioned ``pip`` commands may also be available)
+
+On Windows, use the ``py`` Python launcher in combination with the ``-m``
+switch::
+
+   py -2   -m pip install SomePackage  # default Python 2
+   py -2.7 -m pip install SomePackage  # specifically Python 2.7
+   py -3   -m pip install SomePackage  # default Python 3
+   py -3.4 -m pip install SomePackage  # specifically Python 3.4
+
+.. other questions:
+
+   Once the Development & Deployment part of PPUG is fleshed out, some of
+   those sections should be linked from new questions here (most notably,
+   we should have a question about avoiding depending on PyPI that links to
+   http://packaging.python.org/en/latest/deployment.html#pypi-mirrors-and-caches)
+
+
+Common installation issues
+==========================
+
+Installing into the system Python on Linux
+------------------------------------------
+
+On Linux systems, a Python installation will typically be included as part
+of the distribution. Installing into this Python installation requires
+root access to the system, and may interfere with the operation of the
+system package manager and other components of the system if a component
+is unexpectedly upgraded using ``pip``.
+
+On such systems, it is often better to use a virtual environment or a
+per-user installation when installing packages with ``pip``.
+
+
+Installing binary extensions
+----------------------------
+
+Python has typically relied heavily on source based distribution, with end
+users being expected to compile extension modules from source as part of
+the installation process.
+
+With the introduction of support for the binary ``wheel`` format, and the
+ability to publish wheels for at least Windows and Mac OS X through the
+Python Package Index, this problem is expected to diminish over time,
+as users are more regularly able to install pre-built extensions rather
+than needing to build them themselves.
+
+Some of the solutions for installing `scientific software
+<http://packaging.python.org/en/latest/platforms.html#installing-scientific-packages>`__
+that is not yet available as pre-built ``wheel`` files may also help with
+obtaining other binary extensions without needing to build them locally.
+
+.. seealso::
+
+   `Python Packaging User Guide: Binary Extensions
+   <http://packaging.python.org/en/latest/extensions.html>`__