Somewhere in my archives there’s a story about people putting the ideas put forward by XKCD into some sort of real life application. Well. Here’s another example (previous examples include adults filling their lounge room with colourful balls to make their own ball room).
Somebody did this. And you can follow the progress of the eBay robot on Twitter, and read about the source code here with an update here…
- It runs every day at 8pm (although it was earlier today because I was testing it)
- It gains $1 every day, and has a 1 in 3 chance of buying an item on any particular day. This means that it will save up money to buy some (slightly) more expensive items.
The method it uses to select items:
- It has a bunch of top-level categories it looks in.
- For each of these categories, it searches for the term “Free shipping”, specifying both pay-now and buy-now, sorting by newest listings, with a maximum of 100 items returned per category.
- For each of these items, it filters on buy-now price. It tries to spend at least 50% of its savings.
- For each of the surviving items, it looks up the individual auction details to find its shipping information so it can filter on free shipping. Despite searching for the term ‘free shipping’ to start, only a small number of items have this.
- At this point I have a list of items that match the price requirements, and can be bought with a credit card buy-now.
- I then sort this list by ‘rarity’ – doing a search for the item title, and finding the item that returns the least results. As the objective here is to buy strange and esoteric things, rarity is preferred.
- Finally I buy the rarest item and subtract its cost from the bots savings.
Sounds fun, right? The guy responsible made a couple of changes yesterday:
- It now tries not to buy in categories it’s bought from before. No more stamps! (probably)
- It biases towards auctions with more expensive shipping costs – If you check out the trademe listings, you’ll see there’s quite a lot of items for $1-2, but the more interesting things typically have higher shipping.
- The ‘only bid every 3 days’ rule is gone. Now it will wait until it has at least 20 items that it can possibly buy before making a bid. This is strongly dependent on how much money it has, so it should come to about the same thing.
So far he’s bought some watch batteries, some stickers, and a casio watch. Hooray.