CHAPTER 16
The PyMailCGI Server
“Things to Do When Visiting Chicago”
This chapter is the fifth in our survey of Python Internet programming, and it continues
Chapter 15’s discussion. There, we explored the fundamentals of server-side Common
Gateway Interface (CGI) scripting in Python. Armed with that knowledge, this chapter
moves on to a larger case study that underscores advanced CGI and server-side web
scripting topics.
This chapter presents PyMailCGI—a “webmail” website for reading and sending email
that illustrates security concepts, hidden form fields, URL generation, and more. Be-
cause this system is similar in spirit to the PyMailGUI program we studied in Chap-
ter 14, this example also serves as a comparison of the web and nonweb application
models. This case study is founded on basic CGI scripting, but it implements a complete
website that does something more useful than Chapter 15’s examples.
As usual in this book, this chapter splits its focus between application-level details and
Python programming concepts. For instance, because this is a fairly large case study,
it illustrates system design concepts that are important in actual projects. It also says
more about CGI scripts in general: PyMailCGI expands on the notions of state retention
and security concerns and encryption.
The system presented here is neither particularly flashy nor feature rich as websites go
(in fact, the initial cut of PyMailCGI was thrown together during a layover at Chicago’s
O’Hare airport). Alas, you will find neither dancing bears nor blinking lights at this
site. On the other hand, it was written to serve a real purpose, speaks more to us about
CGI scripting, and hints at just how far Python server-side programs can take us. As
outlined at the start of this part of the book, there are higher-level frameworks, systems,
and tools that build upon ideas we will apply here. For now, let’s have some fun with
Python on the Web.1229Do
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