TweetFollow Us on Twitter

Mac in the Shell-Python on the Mac: PyObjC

Volume Number: 25
Issue Number: 06
Column Tag: Mac in the Shell

Mac in the Shell-Python on the Mac: PyObjC

Writing native Cocoa apps using Python

by Edward Marczak


Over the last few months, we've been covering the basics of Python. Aside from a few OS X-specific issues raised in the first article (how to get the built-in docs working, etc.), you could really take the lessons learned anywhere - Linux, Windows, or any platform where you find a Python runtime. We needed those basics - and we have more to cover, certainly. However, this is MacTech. There's plenty that one can do with some very basic Python and Python/Objective-C bridge, letting you tap into Cocoa. Cocoa? Isn't that reserved for Obj-C developers? Nope. While MacTech has covered this concept before (Scott Corely, "Python Cocoa: Delicious," February 2009), I'd like to put together the lessons learned in this column along with a more utilitarian approach.

Read The Fine Manual

Anytime we're working with Cocoa and the technologies in OS X, we'll probably be pouring through the developer references at You'll need an ADC account to do so. Even the free variety will do, so, go sign up now if you haven't already!

Once you're logged into the Developer Connection, head to the developer docs at More often than not, you'll search on the topic you're after. Sometimes, you find good documentation spread out over several categories. Today, we'll be looking at getting information out of Address Book. True to form, the docs are somewhat spread out. I'll make reference to each as I use it. In short, for now, just search on "address book".

Translating Obj-C

First, why would we want to do this? There are certainly cases when developing for OS X where straight Obj-C is the right choice. However, I'm taking this from a System Administrator's point of view. Often, a System Administrator is already writing basic scripts in bash. I love bash, but there's only so far that it'll get you without becoming painful. If you're writing a script in bash and it passes the 4 functions milestone, it may be time to consider a language more suited to your task. For example, bash isn't really great with databases.

Sure, you can use the mysql binary, pipe the output to awk, and manipulate results from there. But is that the best use of your time and talent? Ever deal with arrays in bash? Pain. While I may recommend Python or Ruby as a step up in general, these languages are made even more special under OS X thanks to Apple's inclusion of an Obj-C bridge. BridgeSupport opens up OS X's native APIs to Python, Ruby and JavaScript. This is available and standard on every Mac running 10.5 or higher. (10.4 support is available, but you'll need to install it yourself, which is outside the scope of this article). BridgeSupport deals with all of the behind-the-scenes work of converting between Python and the native frameworks. The first challenge to this technique is interpreting the documentation. We're going to code all of this in Python, and the docs are directed at people writing in C and Objective-C. Anyone remember having to translate Mac Toolbox API calls from Pascal to C? I digress...

Now that we've covered Python classes, you know about sending a message to an object using dot notation. In last month's column, the BankClass example class contained deposit and withdraw methods. A new class could be created and a method called in the following manner:

acct = Account('Joan', 'Smith')    # Create new account
acct1.Deposit(50)       # Note use of class method here

However, if we got this information from Apple's developer documentation, you'd see something like this:

[acct1 Deposit:50]

This was covered in depth in the "Python Cocoa: Delicious" article referenced earlier, but I'll cover the basic rules here.

As you can see, Obj-C uses square brackets to send messages to objects. The easiest call to translate is a simple message with no parameters. This:

[object message];

in Python becomes:


When a method takes parameters, Obj-C places them in-line:

[object message:40 key:50];

Python keeps its usual format here, separating the method name and parameters. Each message and parameter gains a trailing underscore character:


Essentially, each colon is replaced by an underscore - even if there's only one parameter. For example:


To instantiate an objective-c class in the first place is fairly straightforward.

object = NSObject.alloc().init()

Let's see all of this in action.

Reading the Address Book

The beauty of using a language like Python is that you can author in any editor you like, save and run. This skips the compile/link phase so familiar to Obj-C developers. So, pull up your favorite editor-remember, too, that most editors will be able to recognize Python code and syntax color, indent properly and so on, for you-and let's go.

Contained in /System/Library/Frameworks/Python.frame-work/ are the modules that Python uses for BridgeSupport. These can simply be imported into Python. First thing is first, our magic shebang line:

#!/usr/bin/env python

(Remember, if you have multiple versions of python on your system for some reason, under 10.5, the built-in BridgeSupport only works with Python 2.5. If you need you need to explicitly call that version, then do so). From here, we'll import the AddressBook framework:

from AddressBook import *

It's rare that I like or use the 'from blah import *' style, but there are times when it makes perfect sense. This, I feel, is one of them. We talked extensively about imports and namespaces in previous articles.

Let's create a new instance of an address book object:

aBook = ABAddressBook.sharedAddressBook()

Painless, right? This returns the address book for the logged-in user. Keeping this simple, let's grab the 'me' card for the logged in user and print it out:

myRecord =
print myRecord

That's it! In 3 lines of code, we get a good amount of information. Here's the output:

ABPerson (0x1ab0a40) {
   ABPersonFlags  : 0
   ABRelatedNames : {
      *  child  Edward R Marczak
   Address       : {
      *  work  {
    City = Anytown;
    Country = USA;
    CountryCode = us;
    State = AA;
    Street = "555 Any Street";
    ZIP = 11111;
   AIMInstant     : {
      *  home  myaim
   Creation       : 2005-10-28 09:45:40 -0400
   Email          : {
      *  work
   First          : Edward
   JobTitle       : Owner
   Last           : Marczak
   Middle         : R
   Modification   : 2009-01-14 11:11:25 -0500
   Organization   : Radiotope
   Phone          : {
      *  mobile  555-555-5185
        home    555 555-5370
        main    555-555-5489
   Title          : Mr.
   Unique ID      : B3AD0F6B-4AB8-4E84-82C4-BF1EB7475659:ABPerson

Each of the properties in the record can be accessed and iterated over individually. Each property has a unique name used for this purpose. An illuminating method of discovering this, besides the Apple documentation is to use the dir() function that we've seen previously. Save your work and open a new document that contains this simple code:

#!/usr/bin/env python
import AddressBook
x = dir(AddressBook)
for i in x:
  print i

When you run it, you'll get an absolute ton of output, so pipe it through less or use a GUI editor that can run the code in its own window. It'll look like this:


This lists every function and constant definition in the framework. In this case, we're interested in the block where each constant has the 'kAB' prefix. Each of these properties represents a potential field in the address book record - not all must be present. So, how can we tell which fields are present in a given record? We can ask. Back to our original code!

Here's a complete Python solution to dumping the current user's Address Book, I'll explain the parts not yet covered after this code listing.

Listing 1:

#!/usr/bin/env python
from AddressBook import *
aBook = ABAddressBook.sharedAddressBook()
for person in aBook.people():
  properties = person.allProperties()
  for prop in properties:
    if prop == "":
    elif prop == "":
    print prop, ":", person.valueForProperty_(prop)
  print '-'*60

The people() method returns an array (an NSArray, specifically-the Obj-C Bridge deals with converting between the Obj-C types and Python types). We've previously covered Python for loops, and this one is no different. This loop iterates over each entry returned by the people() method, assigning it to person in each iteration.

With each person, we use the allProperties() method to determine the properties contained in that record. Then, we use another for loop to print only those properties. Note the if statement in this block: there are two properties present in each record that we're really not going to do anything with. Using a continue statement lets us restart the loop at the top.

Now, this isn't going to win any coding competitions, but look at how simple it is. No compiler or special IDE was needed to generate or run any of this.

What Happened? (Maybe)

Some of you may have seen an error pop up while running this program. Something about a "UnicodeDecodeError". What happened? This, partially, is the old-school Unix ASCII-ness colliding with modern sensibilities. You'll only see this error if one of your address book entries has Unicode characters in it (accent marks, Asian/Hebrew/Russian character sets and so on). Well, OS X is built to deal with this. Now, this depends on the environment in which you ran this. should actually have no problem as it's Unicode compliant. Surprisingly, some GUI text editors still don't handle Unicode properly, or, just need a little help. One thing you can do is give the interpreter a little hint: immediately following the magic shebang line (#!/usr/bin/env python), include the following:

# encoding: utf-8

This explicitly sets the encoding of the document. Additionally, Python itself has built-in support for Unicode strings. When printing a string, prefix it with 'u' to specify Unicode output. Like this:

print u'This is a Unicode string'

If you're printing a variable, it's similarly easy:

print u'%s' % (variable)

This is just one of those things that OS X users expect, and script authors need to bear in mind. Kind of like spaces in filenames...


There are actually a few more things we can cover about the Obj-C Bridge and its use in Python. However, we accomplished our goal for this month, and I hope you can see how easy some of these basic tasks are. You'll find that there are often several ways of approaching the code when using BridgeSupport. The methods used in this article are the most appropriate for the task at hand. See the References section below for the specific AddressBook documentation that I used to determine the bulk of this.

If we were more ambitious here, we could certainly do more with the data returned. Like write it out as a CSV file. AddressBook also supports group information, which I actually use fairy often, but that's a topic for next month.

Media of the month: I know, I usually suggest a good book, movie or music CD here, but this month is a little different. This month's suggestion is the outdoors - don't forget about it! Seriously, I'm not really a 'sun person,' but it is nice to take a walk with no laptop/phone/electronic device. Take a bike ride. Have a picnic. Take a (real) hike. Experience it. Just don't forget that there's a world outside of the LCD that we often sit a foot or two away from.

Hopefully, you're reading this at Apple's (sold out, again!) WWDC. Most of us from MacTech are here too (and you may have received this issue while on line for the Keynote - welcome!). Ping us, stop us in the halls - just say hello! See you next month.


"Address Book Programming Guide for Mac OS X,"

"ABAddressBook Class Objective-C Reference," h

"ABPerson C Reference,"

Ed Marczak is the Executive Editor for MacTech Magazine, and has been lucky enough to have ridden the computing and technology wave from early on. From teletype computing to MVS to Netware to modern OS X, his interest was piqued. He has also been fortunate enough to come into contact with some of the best minds in the business. Ed spends his non-compute time with his wife and two daughters.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Dash 3.4.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
RapidWeaver 7.1.7 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
Printopia 2.1.22 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
SteerMouse 5.0 - Powerful third-party mo...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
Arq 5.5.1 - Online backup to Google Driv...
Arq is super-easy online backup for Mac and Windows computers. Back up to your own cloud account (Amazon Cloud Drive, Google Drive, Dropbox, OneDrive, Google Cloud Storage, any S3-compatible server... Read more
Slack 2.3.0 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.3.0: Note: Now requires OS X 10.8 or later New The app... Read more
Cocktail 10.1 - General maintenance and...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Firefox 49.0.2 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Art Text 3.1 - $49.99
Art Text is graphic design software to create stunning illustrations, such as badges, flyers, logos, social headers and icons, text mockups, website graphics and buttons, picture captions, word art,... Read more
AirRadar 3.1.9 - $9.95
With AirRadar, scanning for wireless networks is now easier and more personalized! It allows you to scan for open networks and tag them as favourites or filter them out. View detailed network... Read more

Latest Forum Discussions

See All

Oh...Sir! The Insult Simulator (Games)
Oh...Sir! The Insult Simulator 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
WitchSpring2 (Games)
WitchSpring2 1.27 Device: iOS Universal Category: Games Price: $3.99, Version: 1.27 (iTunes) Description: This is the story of Luna, the Moonlight Witch as she sets out into the world. This is a sequel to Witch Spring. Witch Spring 2... | Read more »
4 popular apps getting a Halloween makeo...
'Tis the season for all things spooky. So much, so, in fact, that even apps are getting into the spirt of things, dressing up in costume and spreading jack o' lanterns all about the place. These updates bring frightening new character skins, scary... | Read more »
Pokémon GO celebrates Halloween with can...
The folks behind Pokémon GO have some exciting things planned for their Halloween celebration, the first in-game event since it launched back in July. Starting October 26 and ending on November 1, trainers will be running into large numbers of... | Read more »
Best Fiends Forever Guide: How to collec...
The fiendship in Seriously's hit Best Fiends has been upgraded this time around in Best Fiends Forever. It’s a fast-paced clicker with lots of color and style--kind of reminiscent of a ‘90s animal mascot game like Crash Bandicoot. The game... | Read more »
5 apps for the budding mixologist
Creating your own cocktails is something of an art form, requiring a knack for unique tastes and devising interesting combinations. It's easy to get started right in your own kitchen, though, even if you're a complete beginner. Try using one of... | Read more »
5 mobile strategy games to try when you...
Strategy enthusiasts everywhere are celebrating the release of Civilization VI this week, and so far everyone seems pretty satisfied with the first full release in the series since 2010. The series has always been about ultra-addictive gameplay... | Read more »
Popclaire talk to us about why The Virus...
Humanity has succumbed to a virus that’s spread throughout the world. Now the dead have risen with a hunger for human flesh, and all that remain are a few survivors. One of those survivors has just called you for help. That’s the plot in POPCLAIRE’... | Read more »
Oceans & Empires preview build sets...
Hugely ambitious sea battler Oceans & Empires is available to play in preview form now on Google Play - but download it quickly, as it’s setting sail away in just a few days. [Read more] | Read more »
Rusty Lake: Roots (Games)
Rusty Lake: Roots 1.1.4 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.4 (iTunes) Description: James Vanderboom's life drastically changes when he plants a special seed in the garden of the house he has inherited.... | Read more »

Price Scanner via

Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
64GB Apple TV on sale for $159, save $40
Best Buy has the 64GB Apple TV on sale for $40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store price may... Read more
EyeQue Introduces iOS And Android Based Advan...
Affordable vision technologies developers EyeQue have announced what they claim to be the world’s most advanced intelligent vision solution, pitched as enabling anyone, anywhere to easily and... Read more
Smartwatch Market Tanks, Declining 51.6% in 2...
The worldwide smartwatch market experienced a round of growing pains in the third quarter of 2016 (3Q16), resulting in a year-over-year decline in shipment volumes. According to data from the... Read more
CAZE announces Ultra Thin Glass Screen Protec...
Hong Kong based CAZE has announced its first ultra thin glass screen protector, the Glazz Pro for iPhone 7/7 Plus. Glazz Pro is made from chemically reinforced glass with an anti-fingerprint... Read more
11-inch MacBook Airs on sale for up to $120 o...
Newegg has 11″ MacBook Airs on sale for up to $120 off MSRP. Shipping is free: - 11″ 1.6GHz/128GB MacBook Air: $799.99 $100 off MSRP - 11″ 1.6GHz/256GB MacBook Air: $979 $120 off MSRP Read more
Up to $300 off Macs, $20 off iPads with Apple...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Apple’s Thursday “Hello Again” Event A Largel...
KGI Securities analyst Ming-Chi Kuo, who has a strong record of Apple hardware prediction accuracy, forecasts in a new note to investors released late last week that a long-overdue redo of the... Read more
12-inch Retina MacBooks on sale for $100 off...
Amazon has 2016 12″ Apple Retina MacBooks on sale for $100 off MSRP. Shipping is free: - 12″ 1.1GHz Silver Retina MacBook: $1199.99 $100 off MSRP - 12″ 1.1GHz Gold Retina MacBook: $1199.99 $100 off... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 52812872 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Solutions Read more
Lead *Apple* Solutions Consultant - Apple (...
# Lead Apple Solutions Consultant Job Number: 52812906 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Lead ASC is an Read more
*Apple* Retail - Multiple Positions- Towson,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Software Engineering Intern: Integration / QA...
Job Summary Apple is currently seeking enthusiastic interns who can work full-time for a minimum of 12-weeks between Fall 2015 and Summer 2016. Our software Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.