4. Using Python on a Macintosh¶

Author:	Bob Savage <bobsavage@mac.com>

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

4.1. Getting and Installing MacPython¶

Mac OS X 10.8 comes with Python 2.7 pre-installed by Apple. If you wish, youare invited to install the most recent version of Python 3 from the Pythonwebsite (http://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 availablethere.

What you get after installing is a number of things:

AMacPython3.3 folder in yourApplications folder. In hereyou find IDLE, the development environment that is a standard part of officialPython distributions; PythonLauncher, which handles double-clicking Pythonscripts from the Finder; and the “Build Applet” tool, which allows you topackage Python scripts as standalone applications on your system.
A framework/Library/Frameworks/Python.framework, which includes thePython executable and libraries. The installer adds this location to your shellpath. To uninstall MacPython, you can simply remove these three things. Asymlink to the Python executable is placed in /usr/local/bin/.

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 areApple-controlled and are used by Apple- or third-party software. Remember thatif you choose to install a newer Python version from python.org, you will havetwo different but functional Python installations on your computer, so it willbe 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 youare completely new to Python you should start reading the tutorial introductionin that document.

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

4.1.1. How to run a Python script¶

Your best way to get started with Python on Mac OS X is through the IDLEintegrated development environment, see sectionThe IDE and use the Help menuwhen the IDE is running.

If you want to run Python scripts from the Terminal window command line or fromthe Finder you first need an editor to create your script. Mac OS X comes with anumber of standard Unix command line editors,vim andemacs among them. If you want a more Mac-like editor,BBEdit orTextWrangler from Bare Bones Software (seehttp://www.barebones.com/products/bbedit/index.shtml) are good choices, as isTextMate (seehttp://macromates.com/). Other editors includeGvim (http://macvim.org) andAquamacs(http://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 toPythonLauncher
SelectPythonLauncher as the default application to open yourscript (or any .py script) through the finder Info window and double-click it.PythonLauncher has various preferences to control how your script islaunched. Option-dragging allows you to change these for one invocation, or useits Preferences menu to change things globally.

4.1.2. Running scripts with a GUI¶

With older versions of Python, there is one Mac OS X quirk that you need to beaware 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. Usepythonwinstead ofpython to start such scripts.

With Python 3.3, you can use eitherpython orpythonw.

4.1.3. Configuration¶

Python on OS X honors all standard Unix environment variables such asPYTHONPATH, but setting these variables for programs started from theFinder 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 Document QA1067 for details.

For more information on installation Python packages in MacPython, see sectionInstalling Additional Python Packages.

4.2. The IDE¶

MacPython ships with the standard IDLE development environment. A goodintroduction to using IDLE can be found athttp://hkn.eecs.berkeley.edu/~dyoo/python/idle_intro/index.html.

4.3. Installing Additional Python Packages¶

There are several methods to install additional Python packages:

Packages can be installed via the standard Python distutils mode (pythonsetup.pyinstall).
Many packages can also be installed via thesetuptools extensionorpip wrapper, seehttp://www.pip-installer.org/.

4.4. 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 isthe foundation of most modern Mac development. Information on PyObjC isavailable fromhttp://pyobjc.sourceforge.net.

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

wxPython is another popular cross-platform GUI toolkit that runs natively onMac OS X. Packages and documentation are available fromhttp://www.wxpython.org.

PyQt is another popular cross-platform GUI toolkit that runs natively on MacOS X. More information can be found athttp://www.riverbankcomputing.co.uk/software/pyqt/intro.

4.5. Distributing Python Applications on the Mac¶

The “Build Applet” tool that is placed in the MacPython 3.3 folder is fine forpackaging small Python scripts on your own machine to run as a standard Macapplication. This tool, however, is not robust enough to distribute Pythonapplications to other users.

The standard tool for deploying standalone Python applications on the Mac ispy2app. More information on installing and using py2app can be foundathttp://undefined.org/python/#py2app.