5. Using Python on macOS
************************

This document aims to give an overview of macOS-specific behavior you
should know about to get started with Python on Mac computers. Python
on a Mac running macOS is very similar to Python on other Unix-derived
platforms, but there are some differences in installation and some
features.

There are various ways to obtain and install Python for macOS. Pre-
built versions of the most recent versions of Python are available
from a number of distributors. Much of this document describes use of
the Pythons provided by the CPython release team for download from the
python.org website. See Alternative distributions for some other
options.


5.1. Using Python for macOS from "python.org"
=============================================


5.1.1. Installation steps
-------------------------

For current Python versions (other than those in "security" status),
the release team produces a **Python for macOS** installer package for
each new release. A list of available installers is provided on the
macOS downloads page. We recommend using the most recent supported
Python version where possible. Current installers provide a universal2
binary build of Python which runs natively on all Macs (Apple Silicon
and Intel) that are supported by a wide range of macOS versions,
currently typically from at least **macOS 10.15 Catalina** on.

The downloaded file is a standard macOS installer package file
(".pkg"). File integrity information (such as checksum, size, and
Sigstore signature) for each file is included on the release download
page. Installer packages and their contents are signed and notarized
with "Python Software Foundation" Apple Developer ID certificates to
meet macOS Gatekeeper requirements.

For a default installation, double-click on the downloaded installer
package file. This should launch the standard macOS Installer app and
display the first of several installer steps.

[image]

Clicking on the **Continue** button brings up the **Read Me** for this
installer. Besides other important information, the **Read Me**
documents which Python version is going to be installed and on what
versions of macOS it is supported. You may need to scroll through to
read the whole file. By default, this **Read Me** will also be
installed in "/Applications/Python 3.15/" and available to read
anytime.

[image]

Clicking on **Continue** proceeds to display the license for Python
and for other included software. You will then need to **Agree** to
the license terms before proceeding to the next step. This license
file will also be installed and available to be read later.

[image]

After the license terms are accepted, the next step is the
**Installation Type** display. For most uses, the standard set of
installation operations is appropriate.

[image]

By pressing the **Customize** button, you can choose to omit or select
certain package components of the installer. Click on each package
name to see a description of what it installs. For details of the
optional free-threaded feature, which is installed by default, see
Installing free-threaded binaries.

[image]

In either case, clicking **Install** will begin the install process by
asking permission to install new software. A macOS user name with
"Administrator" privilege is needed as the installed Python will be
available to all users of the Mac.

When the installation is complete, the **Summary** window will appear.

[image]

Double-click on the **Install Certificates.command** icon or file in
the "/Applications/Python 3.15/" window to complete the installation.

[image]

This will open a temporary **Terminal** shell window that will use the
new Python to download and install SSL root certificates for its use.

[image]

If "Successfully installed certifi" and "update complete" appear in
the terminal window, the installation is complete. Close this terminal
window and the installer window.

A default install will include:

* A "Python 3.15" 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 macOS 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. Symlinks to the Python executable are placed in
  "/usr/local/bin/".

Note:

  Recent versions of macOS include a **python3** command in
  "/usr/bin/python3" that links to a usually older and incomplete
  version of Python provided by and for use by the Apple development
  tools, **Xcode** or the **Command Line Tools for Xcode**. You should
  never modify or attempt to delete this installation, as it is Apple-
  controlled and is used by Apple-provided or third-party software.
  If you choose to install a newer Python version from "python.org",
  you will have two different but functional Python installations on
  your computer that can co-exist. The default installer options
  should ensure that its **python3** will be used instead of the
  system **python3**.


5.1.2. How to run a Python script
---------------------------------

There are two ways to invoke the Python interpreter. If you are
familiar with using a Unix shell in a terminal window, you can invoke
"python3.15" or "python3" optionally followed by one or more command
line options (described in Command line and environment). The Python
tutorial also has a useful section on using Python interactively from
a shell.

You can also invoke the interpreter through an integrated development
environment. IDLE — Python editor and shell is a basic editor and
interpreter environment which is included with the standard
distribution of Python. **IDLE** includes a Help menu that allows you
to access Python documentation. If you are completely new to Python,
you can read the tutorial introduction in that document.

There are many other editors and IDEs available, see Editors and IDEs
for more information.

To run a Python script file from the terminal window, you can invoke
the interpreter with the name of the script file:

   "python3.15" "myscript.py"

To run your script from the Finder, you can either:

* 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.

Be aware that running the script directly from the macOS Finder might
produce different results than when running from a terminal window as
the script will not be run in the usual shell environment including
any setting of environment variables in shell profiles. And, as with
any other script or program, be certain of what you are about to run.


5.2. Alternative distributions
==============================

Besides the standard "python.org" for macOS installer, there are
third-party distributions for macOS that may include additional
functionality. Some popular distributions and their key features:

ActivePython
   Installer with multi-platform compatibility, documentation

Anaconda
   Popular scientific modules (such as numpy, scipy, and pandas) and
   the "conda" package manager.

Homebrew
   Package manager for macOS including multiple versions of Python and
   many third-party Python-based packages (including numpy, scipy, and
   pandas).

MacPorts
   Another package manager for macOS including multiple versions of
   Python and many third-party Python-based packages. May include pre-
   built versions of Python and many packages for older versions of
   macOS.

Note that distributions might not include the latest versions of
Python or other libraries, and are not maintained or supported by the
core Python team.


5.3. Installing additional Python packages
==========================================

Refer to the Python Packaging User Guide for more information.


5.4. GUI programming
====================

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

The standard Python GUI toolkit is "tkinter", based on the cross-
platform Tk toolkit (https://www.tcl.tk). A macOS-native version of Tk
is included with the installer.

*PyObjC* is a Python binding to Apple’s Objective-C/Cocoa framework.
Information on PyObjC is available from pyobjc.

A number of alternative macOS GUI toolkits are available including:

* 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. Advanced topics
====================


5.5.1. Installing free-threaded binaries
----------------------------------------

Added in version 3.13.

Changed in version 3.15: Free-threading support is now installed by
default.

The "python.org" Python for macOS installer package installs, by
default, an additional build of Python 3.15 that supports *free
threading* (running with the *global interpreter lock* disabled).
Check the release page on "python.org" for possible updated
information.

The free-threaded mode is working and continues to be improved, but
there is some additional overhead in single-threaded workloads
compared to the regular build. Additionally, third-party packages, in
particular ones with an *extension module*, may not be ready for use
in a free-threaded build, and will re-enable the *GIL*. As of Python
3.15, free-threading support is installed by default. It is packaged
as a separate install option, which can be deselected by clicking the
**Customize** button on the **Installation Type** step of the
installer as described above.

[image]

If the box next to the **Free-threaded Python** package name is
checked (as it is by default), a separate "PythonT.framework" will
also be installed alongside the normal "Python.framework" in
"/Library/Frameworks". This configuration allows a free-threaded
Python 3.15 build to co-exist on your system with a traditional (GIL
only) Python 3.15 build with minimal risk while installing or testing.
This installation layout may change in future releases.

Known cautions and limitations:

* The **UNIX command-line tools** package, which is selected by
  default, will install links in "/usr/local/bin" for "python3.15t",
  the free-threaded interpreter, and "python3.15t-config", a
  configuration utility which may be useful for package builders.
  Since "/usr/local/bin" is typically included in your shell "PATH",
  in most cases no changes to your "PATH" environment variable should
  be needed to use "python3.15t".

* For this release, the **Shell profile updater** package and the
  "Update Shell Profile.command" in "/Applications/Python 3.15/" do
  not support the free-threaded package.

* The free-threaded build and the traditional build have separate
  search paths and separate "site-packages" directories so, by
  default, if you need a package available in both builds, it may need
  to be installed in both. The free-threaded package will install a
  separate instance of **pip** for use with "python3.15t".

  * To install a package using **pip** without a **venv**:

       python3.15t -m pip install <package_name>

* When working with multiple Python environments, it is usually safest
  and easiest to create and use virtual environments. This can avoid
  possible command name conflicts and confusion about which Python is
  in use:

     python3.15t -m venv <venv_name>

  then **activate**.

* To run a free-threaded version of IDLE:

     python3.15t -m idlelib

* The interpreters in both builds respond to the same PYTHON
  environment variables which may have unexpected results, for
  example, if you have "PYTHONPATH" set in a shell profile. If
  necessary, there are command line options like "-E" to ignore these
  environment variables.

* The free-threaded build links to the third-party shared libraries,
  such as "OpenSSL" and "Tk", installed in the traditional framework.
  This means that both builds also share one set of trust certificates
  as installed by the **Install Certificates.command** script, thus it
  only needs to be run once.

* If you cannot depend on the link in "/usr/local/bin" pointing to the
  "python.org" free-threaded "python3.15t" (for example, if you want
  to install your own version there or some other distribution does),
  you can explicitly set your shell "PATH" environment variable to
  include the "PythonT" framework "bin" directory:

     export PATH="/Library/Frameworks/PythonT.framework/Versions/3.15/bin":"$PATH"

  The traditional framework installation by default does something
  similar, except for "Python.framework". Be aware that having both
  framework "bin" directories in "PATH" can lead to confusion if there
  are duplicate names like "python3.15" in both; which one is actually
  used depends on the order they appear in "PATH". The "which
  python3.x" or "which python3.xt" commands can show which path is
  being used. Using virtual environments can help avoid such
  ambiguities. Another option might be to create a shell **alias** to
  the desired interpreter, like:

     alias py3.15="/Library/Frameworks/Python.framework/Versions/3.15/bin/python3.15"
     alias py3.15t="/Library/Frameworks/PythonT.framework/Versions/3.15/bin/python3.15t"


5.5.2. Installing using the command line
----------------------------------------

If you want to use automation to install the "python.org" installer
package (rather than by using the familiar macOS **Installer** GUI
app), the macOS command line **installer** utility lets you select
non-default options, too. If you are not familiar with **installer**,
it can be somewhat cryptic (see **man installer** for more
information). As an example, the following shell snippet shows one way
to do it, using the "3.15.0b2" release and deselecting the free-
threaded interpreter option:

   RELEASE="python-3.150b2-macos11.pkg"

   # download installer pkg
   curl -O https://www.python.org/ftp/python/3.15.0/${RELEASE}

   # create installer choicechanges to customize the install:
   #    disable the PythonTFramework-3.15 package
   #    while accepting the other defaults (install all other packages)
   cat > ./choicechanges.plist <<EOF
   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   <plist version="1.0">
   <array>
           <dict>
                   <key>attributeSetting</key>
                   <integer>0</integer>
                   <key>choiceAttribute</key>
                   <string>selected</string>
                   <key>choiceIdentifier</key>
                   <string>org.python.Python.PythonTFramework-3.15</string>
           </dict>
   </array>
   </plist>
   EOF

   sudo installer -pkg ./${RELEASE} -applyChoiceChangesXML ./choicechanges.plist -target /

After a default install, you can test that both builds are available
with something like:

   $ # test that the free-threaded interpreter was installed if the Unix Command Tools package was enabled
   $ /usr/local/bin/python3.15t -VV
   Python 3.15.0b2 free-threading build (v3.15.0b2:3a83b172af, Jun  5 2024, 12:57:31) [Clang 15.0.0 (clang-1500.3.9.4)]
   $ #    and the traditional interpreter
   $ /usr/local/bin/python3.15 -VV
   Python 3.15.0b2 (v3.15.0b2:3a83b172af, Jun  5 2024, 12:50:24) [Clang 15.0.0 (clang-1500.3.9.4)]
   $ # test that they are also available without the prefix if /usr/local/bin is on $PATH
   $ python3.15t -VV
   Python 3.15.0b2 free-threading build (v3.15.0b2:3a83b172af, Jun  5 2024, 12:57:31) [Clang 15.0.0 (clang-1500.3.9.4)]
   $ python3.15 -VV
   Python 3.15.0b2 (v3.15.0b2:3a83b172af, Jun  5 2024, 12:50:24) [Clang 15.0.0 (clang-1500.3.9.4)]

Note:

  Current "python.org" installers only install to fixed locations like
  "/Library/Frameworks/", "/Applications", and "/usr/local/bin". You
  cannot use the **installer** "-domain" option to install to other
  locations.


5.5.3. 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.


5.5.4. 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 python.org Help page has links to many useful resources. The
Pythonmac-SIG mailing list is another support resource specifically
for Python users and developers on the Mac.
