5. 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 integrated development environment (IDE) and the
Package Manager that are worth pointing out.


5.1. Getting and Installing Python
==================================

macOS used to come with Python 2.7 pre-installed between versions 10.8
and 12.3. You are invited to install the most recent version of Python
3 from the Python website. A current "universal2 binary" build of
Python, which runs natively on the Mac's new Apple Silicon and legacy
Intel processors, is available there.

What you get after installing is a number of things:

* A "Python 3.13" folder in your "Applications" folder. In here you
  find IDLE, the development environment that is a standard part of
  official Python distributions; and **Python Launcher**, which
  handles double-clicking Python scripts from the Finder.

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

Not:

  On macOS 10.8-12.3, the Apple-provided build of Python is installed
  in "/System/Library/Frameworks/Python.framework" and
  "/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.


5.1.1. 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 The 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, **vim** **nano** among them. If you want a more Mac-like
editor, **BBEdit** from Bare Bones Software (see
https://www.barebones.com/products/bbedit/index.html) are good
choices, as is **TextMate** (see https://macromates.com). Other
editors include **MacVim** (https://macvim.org) and **Aquamacs**
(https://aquamacs.org).

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

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

* Drag it to **Python Launcher**.

* Select **Python Launcher** as the default application to open your
  script (or any ".py" script) through the finder Info window and
  double-click it. **Python Launcher** 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.


5.1.2. 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 **pythonw** instead of **python** to start such scripts.

With Python 3.9, you can use either **python** or **pythonw**.


5.1.3. Configuration
--------------------

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

For more information on installation Python packages, see section
Installing Additional Python Packages.


5.2. The IDE
============

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


5.3. Installing Additional Python Packages
==========================================

This section has moved to the Python Packaging User Guide.


5.4. GUI Programming
====================

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 pyobjc.

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

A number of alternative macOS GUI toolkits are available:

* PySide: Official Python bindings to the Qt GUI toolkit.

* PyQt: Alternative Python bindings to Qt.

* Kivy: A cross-platform GUI toolkit that supports desktop and mobile
  platforms.

* Toga: Part of the BeeWare Project; supports desktop, mobile, web and
  console apps.

* wxPython: A cross-platform toolkit that supports desktop operating
  systems.


5.5. Distributing Python Applications
=====================================

A range of tools exist for converting your Python code into a
standalone distributable application:

* py2app: Supports creating macOS ".app" bundles from a Python
  project.

* Briefcase: Part of the BeeWare Project; a cross-platform packaging
  tool that supports creation of ".app" bundles on macOS, as well as
  managing signing and notarization.

* PyInstaller: A cross-platform packaging tool that creates a single
  file or folder as a distributable artifact.


5.5.1. App Store Compliance
---------------------------

Apps submitted for distribution through the macOS App Store must pass
Apple's app review process. This process includes a set of automated
validation rules that inspect the submitted application bundle for
problematic code.

The Python standard library contains some code that is known to
violate these automated rules. While these violations appear to be
false positives, Apple's review rules cannot be challenged. Therefore,
it is necessary to modify the Python standard library for an app to
pass App Store review.

The Python source tree contains a patch file that will remove all code
that is known to cause issues with the App Store review process. This
patch is applied automatically when CPython is configured with the "--
with-app-store-compliance" option.

This patch is not normally required to use CPython on a Mac; nor is it
required if you are distributing an app *outside* the macOS App Store.
It is *only* required if you are using the macOS App Store as a
distribution channel.


5.6. Other Resources
====================

The Pythonmac-SIG 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
