[As of the most recent upgrade of the Seattle Public Library’s website, you can no longer access your checkouts or holds by RSS, so this no longer works. Sad.]

When I was a kid, my mom used to save all of the receipts from the library and when it was time to take the books back, we would check each one off to make sure none were left behind. Nowadays, you can just check the library website, but that can get tedious: log into my account, find out which books I have checked out, find out which books are on hold, long out of my account, log into my wife’s account, repeat. And soon my kids will have accounts too? So much clicking! Ahh! Luckily, the Seattle Public Library offers both your holds list and your checked-out list in RSS/XML format. It was not hard to write a script to download the RSS file, extract the useful information, and display it nicely. For a long time, I ran this once a day using a LaunchAgent on my home computer. This was inefficient, so I finally decided I should understand how cgi scripting works, because up till now php was the only web scripting I had done. Of course, I was embarrassed at how easy cgi scripting really is.

The Python script

The script uses Feed Parser to parse the RSS, which makes things easy. The main idea is this:

feed = feedparser.parse("http://example.com/feed/")
booklist = feed.entries
for book in booklist:
    print book.title    #the title of the RSS entry
    print book.summary  #the summary of the RSS entry

Other than that, the script is doing some basic extraction using str.find and some list sorting.

Making it work as a cgi

This program is the simplest possible cgi script, because it requires no input. The idea behind cgi is that everything that the program outputs is served to the user. The only thing you have to do is begin your output with an html header like this:

print "Content-Type: text/html; charset=UTF-8\n"

Remember that your header should be followed by a blank line, as above. Of course, you should also be careful about catching errors so they aren’t inserted into the html. The script is here: library.cgi