
.. _using-on-mac:

*********************
Using Python on a Mac
*********************

:Author: Bob Savage <bobsavage@mac.com>


Python on a Mac running macOS is in principle very similar to Python on
any other Unix platform, but there are a number of additional features such as
the IDE and the Package Manager that are worth pointing out.

.. _getting-osx:

Getting and Installing MacPython
================================

macOS since version 10.8 comes with Python 2.7 pre-installed by Apple.  If you wish, you
are invited to install the most recent version of Python 3 from the Python
website (https://www.python.org).  A current "universal binary" build of Python,
which runs natively on the Mac's new Intel and legacy PPC CPU's, is available
there.

What you get after installing is a number of things:

* A :file:`Python 3.9` folder in your :file:`Applications` folder. In here
  you find IDLE, the development environment that is a standard part of official
  Python distributions; and PythonLauncher, which handles double-clicking Python
  scripts from the Finder.

* A framework :file:`/Library/Frameworks/Python.framework`, which includes the
  Python executable and libraries. The installer adds this location to your shell
  path. To uninstall MacPython, you can simply remove these three things. A
  symlink to the Python executable is placed in /usr/local/bin/.

The Apple-provided build of Python is installed in
:file:`/System/Library/Frameworks/Python.framework` and :file:`/usr/bin/python`,
respectively. You should never modify or delete these, as they are
Apple-controlled and are used by Apple- or third-party software.  Remember that
if you choose to install a newer Python version from python.org, you will have
two different but functional Python installations on your computer, so it will
be important that your paths and usages are consistent with what you want to do.

IDLE includes a help menu that allows you to access Python documentation. If you
are completely new to Python you should start reading the tutorial introduction
in that document.

If you are familiar with Python on other Unix platforms you should read the
section on running Python scripts from the Unix shell.


How to run a Python script
--------------------------

Your best way to get started with Python on macOS is through the IDLE
integrated development environment, see section :ref:`ide` and use the Help menu
when the IDE is running.

If you want to run Python scripts from the Terminal window command line or from
the Finder you first need an editor to create your script. macOS comes with a
number of standard Unix command line editors, :program:`vim` and
:program:`emacs` among them. If you want a more Mac-like editor,
:program:`BBEdit` or :program:`TextWrangler` from Bare Bones Software (see
http://www.barebones.com/products/bbedit/index.html) are good choices, as is
:program:`TextMate` (see https://macromates.com/). Other editors include
:program:`Gvim` (http://macvim-dev.github.io/macvim/) and :program:`Aquamacs`
(http://aquamacs.org/).

To run your script from the Terminal window you must make sure that
:file:`/usr/local/bin` is in your shell search path.

To run your script from the Finder you have two options:

* Drag it to :program:`PythonLauncher`

* Select :program:`PythonLauncher` as the default application to open your
  script (or any .py script) through the finder Info window and double-click it.
  :program:`PythonLauncher` has various preferences to control how your script is
  launched. Option-dragging allows you to change these for one invocation, or use
  its Preferences menu to change things globally.


.. _osx-gui-scripts:

Running scripts with a GUI
--------------------------

With older versions of Python, there is one macOS quirk that you need to be
aware of: programs that talk to the Aqua window manager (in other words,
anything that has a GUI) need to be run in a special way. Use :program:`pythonw`
instead of :program:`python` to start such scripts.

With Python 3.9, you can use either :program:`python` or :program:`pythonw`.


Configuration
-------------

Python on macOS honors all standard Unix environment variables such as
:envvar:`PYTHONPATH`, but setting these variables for programs started from the
Finder is non-standard as the Finder does not read your :file:`.profile` or
:file:`.cshrc` at startup. You need to create a file
:file:`~/.MacOSX/environment.plist`. See Apple's Technical Document QA1067 for
details.

For more information on installation Python packages in MacPython, see section
:ref:`mac-package-manager`.


.. _ide:

The IDE
=======

MacPython ships with the standard IDLE development environment. A good
introduction to using IDLE can be found at
http://www.hashcollision.org/hkn/python/idle_intro/index.html.


.. _mac-package-manager:

Installing Additional Python Packages
=====================================

There are several methods to install additional Python packages:

* Packages can be installed via the standard Python distutils mode (``python
  setup.py install``).

* Many packages can also be installed via the :program:`setuptools` extension
  or :program:`pip` wrapper, see https://pip.pypa.io/.


GUI Programming on the Mac
==========================

There are several options for building GUI applications on the Mac with Python.

*PyObjC* is a Python binding to Apple's Objective-C/Cocoa framework, which is
the foundation of most modern Mac development. Information on PyObjC is
available from https://pypi.org/project/pyobjc/.

The standard Python GUI toolkit is :mod:`tkinter`, based on the cross-platform
Tk toolkit (https://www.tcl.tk). An Aqua-native version of Tk is bundled with OS
X by Apple, and the latest version can be downloaded and installed from
https://www.activestate.com; it can also be built from source.

*wxPython* is another popular cross-platform GUI toolkit that runs natively on
macOS. Packages and documentation are available from https://www.wxpython.org.

*PyQt* is another popular cross-platform GUI toolkit that runs natively on
macOS. More information can be found at
https://riverbankcomputing.com/software/pyqt/intro.


Distributing Python Applications on the Mac
===========================================

The standard tool for deploying standalone Python applications on the Mac is
:program:`py2app`. More information on installing and using py2app can be found
at https://pypi.org/project/py2app/.


Other Resources
===============

The MacPython mailing list is an excellent support resource for Python users and
developers on the Mac:

https://www.python.org/community/sigs/current/pythonmac-sig/

Another useful resource is the MacPython wiki:

https://wiki.python.org/moin/MacPython

