Using dictionaries rather than complex if-elif-else clauses

Lately, I’ve been using dictionaries as a dispatching mechanism. It seems especially elegant when I face some fairly elaborate switching logic.

For example, instead of:
if a == 1 and b == 1:
log("everything worked!")
commit()


elif a == 1 and b == 0:
log("a good, b bad")
report_that_b_failed()


else:
log("a failed")
report_that_a_failed()

Do this:


d = {
(1, 1): commit,
(1, 0): report_that_b_failed,
(0, 0): report_that_a_failed
}


k = (a, b)
f = d[k]
f()

This approach is also really useful when you face the need to change logic based on runtime values. You can imagine that d might be built after parsing an XML file.

How to have a better cygwin terminal

Cygwin is a wonderful tool. However, I don’t really like the default terminal. This article shows how to set up an rxvt terminal instead.

This is a screenshot of the default cygwin bash prompt:

cropped-dos-terminal.png

Copying and pasting is not intuitive, you can’t stretch the box horizontally, and most importantly, it breaks the illusion that I’m on a Unix box. But a better terminal option exists! When you install cygwin, you can also install the rxvt package. After installing the rxvt package, try this in a DOS window:

C:\cygwin\bin\rxvt.exe -fg gray -bg MidnightBlue -fn "Lucida Console-14" -e bash --login -i

You should see a terminal like this:

cropped-rxvt-terminal

As far as I can tell from my experience, this terminal acts exactly like a regular rxvt terminal on a linux box. I can highlight some text with my mouse, and then paste it by hitting either shift+insert or by hitting the middle mouse button. I can resize the terminal horizontally and vertically.

I set up a taskbar icon so that I can get that rxvt very quickly. The icon before the right-most icon will start an rxvt terminal for me.

startbar

Setting it up was really simple. I made a new shortcut by right-clicking on my desktop, then I copied this text:

C:\cygwin\bin\rxvt.exe -fg gray -bg MidnightBlue -fn "Lucida Console-14" -e bash --login -i

into the target field:

shortcut

Then I hit OK, and then dragged the new shortcut into the taskbar, and that’s it!

Ubuntu and TurboGears

It shouldn’t be so hard to set up turbogears on ubuntu Feisty Fox. The easy_install-2.4 turbogears approach crashes when trying to install Cheetah.

So, here’s a list of everything I had to do:

  • I installed the Ubuntu package for Cheetah: sudo apt-get install python-cheetah
  • Then I could run the easy install: sudo easy_install-2.4 turbogears
  • I edited /etc/apt/sources.list and added multiverse to the list of available packages. In other words, I changed this section:

deb http://archive.ubuntu.com/ubuntu/ feisty universe
deb-src http://archive.ubuntu.com/ubuntu/ feisty universe

to look like this:

deb http://archive.ubuntu.com/ubuntu/ feisty universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ feisty universe multiverse

  • Then I installed the python profiler package: sudo apt-get install python-profiler.
  • I tried installing pysqlite2 through easy_install, but that blew up, so I installed ubuntu package for pysqlite2 instead: sudo apt-get install python-pysqlite2.

Now everything works.