Programming Python, 3rd Edition

What’s a Server-Side CGI Script?

Simply put, CGI scripts implement much of the interaction you typically experience on the Web. They are a standard and widely used mechanism for programming web-based systems and web site interaction. There are other ways to add interactive behavior to web sites with Python, including client-side solutions (e.g., Jython applets and Active Scripting), as well as server-side technologies that build on the basic CGI model (e.g., Python Server Pages, and the Zope, Webware, CherryPy, and Django frameworks). We will discuss such alternatives in Chapter 18.

But by and large, CGI server-side scripts are used to program much of the activity on the Web. They are perhaps the most primitive approach to implementing web sites, and they do not by themselves offer the tools that are often built into larger frameworks. CGI scripts, however, are in many ways the simplest technique for server-side scripting. As a result, they are an ideal way to get started with programming on the server side of the Web. Especially for simpler sites that do not require enterprise-level tools, CGI is sufficient, and can be augmented with additional libraries as needed.

The Script Behind the Curtain

Formally speaking, CGI scripts are programs that run on a server machine and adhere to the Common Gateway Interface—a model for browser/server communications, from which CGI scripts take their name. CGI is an application protocol that web servers use to transfer input data and results between ...