So, you’ve got the shiny new iOS 4.2 on your iPhone 4 and you have enabled AirPrint sharing on your Mac, using either the free Hacktivator or one of the commercial packages. You are very satisfied (albeit a bit doubtful about actually using it in the future), except for one thing: it prints in color, and you really wish it could print in grayscale, because toner is not cheap.

When printing on the Mac this is easy: in any application’s print dialog, you change the specific settings of your printer to convert to grayscale and save a new preset. Then you just select “use last selected preset” and you forget about it, limiting yourself to changing it to color whenever you feel like wasting money (or printing money, if you’re that kind of naughty boy.)

AirPrint, on the other hand, just doesn’t have any setting, aside from the number of copies. You can’t even choose which pages to print. It’s either all or nothing. And it prints in color. It all seems lost, but fear not! OS X’s print subsystem is based on — or rather, it actually is — CUPS, which stands for Common Unix Printing System. Therefore all you need to is fiddling with it to change the actual default settings. How do you do that? It’s very, very simple.

Go to http://localhost:631/ (the CUPS configuration runs via a pseudo-webserver on port 631; don’t worry, this only works on your own machine for your own machine), and click on Administration on top, then click on Manage Printers. Click on the name of the printer in question, and in the Administration pull-down menu choose Set Default Options. What you see now depends on the actual printer you have, but it should very closely resemble the options you get in the OS X print dialog. In my case, the General tab shows a setting called  Color Mode that lets me choose between Color and Grayscale. I set it to the latter, clicked the Set Default Options button, typed in my username and password, and off I went.

Note that you must have administrator rights, and you have use your short username, the one in lowercase with no spaces. It’s the same one that gives the name to your own home folder.

(Many thanks to Marco F. for the input.)

Installing the module alone doesn’t work, because MAMP installs no headers; and copying the headers from the vanilla MySQL distribution doesn’t help either, because a few of the required files are generated on the fly during the installation of MySQL itself.

The solution, it turns out, is relatively simple. Follow along.

Step 1: download the latest MySQL Community Server in DMG format for x86-64 from this page, and install the main package. Worry not: nothing is going to be started on boot, so this is not going to mess with your pre-existing MySQL installation. The package is going to be installed in /usr/local/mysql-5.1.45-osx10.6-x86_64/, with a handy /usr/local/mysql/ symbolic link.

Step 2: download the latest MySQLdb Python module from this page, and unpack it somewhere.

Step 3: set the $PATH environment variable to include /usr/local/mysql. That’s because the module’s setup.py is going to need to call mysql_config, and you want it to find the one you just installed, as it comes with all the stuff it needs.

Step 4: do the classic build and install dance, making sure you prepend the commands with ARCHFLAGS=’-arch x86_64′. This is because you want to compile a 64-bit module.

In short:
tar vxfz MySQL-python-1.2.3c1.tar.gz
cd MySQL-python-1.2.3c1
export PATH=/usr/local/mysql:$PATH
ARCHFLAGS='-arch x86_64' python setup.py build
ARCHFLAGS='-arch x86_64' python setup.py install

If all went fine, you should be able to do this without getting any errors:
octavarium:~ jollino$ python
Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import MySQLdb
>>> print MySQLdb
<module 'MySQLdb' from '/Library/Python/2.6/site-packages/MySQL_python-1.2.3c1-py2.6-macosx-10.6-universal.egg/MySQLdb/__init__.pyc'>

Enjoy!