Python iterators are objects (or functions, using some magic) thatrepeatedly produce values, one at a time, until they getexhausted. Python introduced this general feature to efficientlysupport things like:

for line in fp.readlines():    ... do something with each line ...

Without iterators, .readlines() would have to read the entire fileinto memory, split it up into lines, and return a huge list; now, thiscode only has one line in memory at any given

AJAX is short for 'Asynchronous Javascript And XML', the common termfor the technology behind highly interactive web sites like GoogleMaps and Google Mail. Given that the features AJAX enables (from thelarge to the small) are very appealing to designers, we're pretty muchguaranteed to see more and more use of it on web sites.

But please don't reach for AJAX too fast, because there is such athing as being too interactive.

AJAX's interactivity comes through communication, and communicationtakes

Although I've been programming in Python for a few years now, it keepssurprising me with little bits and pieces. Here's a neat Python languagefeature that I recently used for the first time (discovered originallythrough Bram Cohen's LiveJournal).

A common programming pattern is 'search for a something to work on, butstop if you don't find anything'. In Python one might write it somethinglike this (taken more or less from DWiki 's source):

found = False

Every HTTP reply from a web server can include a Last-Modified: header, which theoretically tells interested parties when the web pagewas last modified. This is really something that works best when theweb server is just sending out static files; when it is generatingdynamic content, like DWiki does, things get interesting.

The major use of Last-Modified: is to decide when a browser already hasa current copy of the web page and doesn't need to fetch it again. Thus,with dynamic pages