One of the projects I’m tackling on sabbatical is a community version of LibraryLookup. The service I wanted to create is described here: an RSS feed that’s updated when a book on your Amazon wishlist becomes available in your local library. Originally I planned to build a simple web application that would register Amazon wishlist IDs and produce custom RSS feeds for each registrant. But as I thought about what would make this service palatable to a community, I saw two problems with that approach:
- Familiarity. Most folks will not be familiar with RSS. If the primary goal is to get people using the service, rather than to evangelize RSS, it should use the more familiar style of email notification.
- Deployability. A web application needs to be hosted somewhere. In most communities, the library won’t be able to host the service on its own infrastructure. But if it’s hosted elsewhere, there will be a (rational) reluctance to take a dependency on that provider.
To address the first concern, I’m doing this as an old-fashioned email-based app. You subscribe or unsubscribe by sending email with a command and a wishlist ID in the Subject: header. And you receive notifications about book availability by way of email.
To address the second concern, I’m doing it as a client-side Python script, so that the only dependency is some version of Python and an Internet connection.
Because a library might not even be able to dedicate an email address for this purpose, I’m exploring the use of Gmail as the communication engine. In order for that to work, Python has to be able to make secure and authenticated POP and SMTP connections. Happily, it can.
The recipe for connecting Python to Gmail’s POP service is trivial:
p = poplib.POP3_SSL(‘pop.gmail.com’)
The recipe for connecting Python to Gmail’s SMTP service is less obvious:
s = smtplib.SMTP(“smtp.gmail.com”)
auth = ‘\x00USERNAME\x00PASSWORD’
eauth = base64.b64encode(auth)
This won’t work with no authentication, but neither will it work with the SMTP module’s login() which uses the wrong authentication type (i.e., LOGIN rather than PLAIN, I think).
Any POP/SMTP servers can be used, of course, so there’s no dependency on Gmail here, but it’s nice to see that Gmail can easily be pressed into service if need be.
It feels retro and trailing-edge to do an email-based app but, in order to make it familiar and deployable that seems like the right approach.