PyMailGUI is a Python program that implements a client-side email processing user interface with the standard Tkinter GUI toolkit. It is presented both as an instance of Python Internet scripting and as a realistically scaled example that ties together other tools we’ve already seen, such as threads and Tkinter GUIs.

Like the pymail console-based program we wrote in Chapter 14, PyMailGUI runs entirely on your local computer. Your email is fetched from and sent to remote mail servers over sockets, but the program and its user interface run locally. As a result, PyMailGUI is called an email client: like pymail , it employs Python’s client-side tools to talk to mail servers from the local machine. Unlike pymail , though, PyMailGUI is a full-featured user interface: email operations are performed with point-and-click operations and advanced mail processing such as attachments and save files is supported.

Like many examples presented in this text, PyMailGUI is a practical, useful program. In fact, I run it on all kinds of machines to check my email while traveling around the world teaching Python classes. Although PyMailGUI won’t put Microsoft Outlook out of business anytime soon, it has two key pragmatic features that have nothing to do with email itself: portability and scriptability, which are attractive features in their own right and they merit a few additional words here.

It’s portable

PyMailGUI runs on any machine with sockets and a Python with Tkinter installed. Because email is transferred with the Python libraries, any Internet connection that supports Post Office Protocol (POP) and Simple Mail Transfer Protocol (SMTP) access will do. Moreover, because the user interface is coded with Tkinter, PyMailGUI should work, unchanged, on Windows, the X Window System (Unix, Linux), and the Macintosh (classic and OS X).

Microsoft Outlook may be a more feature-rich package, but it has to be run on Windows, and more specifically, on a single Windows machine. Because it generally deletes email from a server as it is downloaded and stores it on the client, you cannot run Outlook on multiple machines without spreading your email across all those machines. By contrast, PyMailGUI saves and deletes email only on request, and so it is a bit friendlier to people who check their email in an ad hoc fashion on arbitrary computers.

It’s scriptable

PyMailGUI can become anything you want it to be because it is fully programmable. In fact, this is the real killer feature of PyMailGUI and of open source software like Python in general—because you have full access to PyMailGUI’s source code, you are in complete control of where it evolves from here. You have nowhere near as much control over commercial, closed products like Outlook; you generally get whatever a large company decided you need, along with whatever bugs that company might have introduced.

As a Python script, PyMailGUI is a much more flexible tool. For instance, we can change its layout, disable features, and add completely new functionality quickly by changing its Python source code. Don’t like the mail-list display? Change a fewlines of code to customize it. Want to save and delete your mail automatically as it is loaded? Add some more code and buttons. Tired of seeing junk mail? Add a fewlines of text processing code to the load function to filter spam. These are just a few examples. The point is that because PyMailGUI is written in a high-level, easy-to-maintain scripting language, such customizations are relatively simple, and might even be fun.

At the end of the day, because of such features, this is a realistic Python program that I actually use—both as a primary email tool and as a fallback option when my ISP’s webmail system goes down (which, as I mentioned in the prior chapter, has a way of happening at the worst possible times).* Python scripting is an enabling skill to have.

It’s also worth mentioning that PyMailGUI achieves its portability and scriptability, and implements a full-featured email interface along the way, in roughly 2,200 lines of program code. It may not have all the bells and whistles of some commercial products, but the fact that it gets as close as it does in so few lines of code is a testament to the power of both the Python language and its libraries.