Programming Python, 3rd Edition

Climbing the CGI Learning Curve

Now that we’ve looked at setup issues, it’s time to get into concrete programming details. This section is a tutorial that introduces CGI coding one step at a time—from simple, noninteractive scripts to larger programs that utilize all the common web page user input devices (what we called widgets in the Tkinter GUI chapters in Part III).

Along the way, we’ll also explore the core ideas behind server-side scripting. We’ll move slowly at first, to learn all the basics; the next chapter will use the ideas presented here to build up larger and more realistic web site examples. For now, let’s work through a simple CGI tutorial, with just enough HTML thrown in to write basic server-side scripts.

A First Web Page

As mentioned, CGI scripts are intimately bound up with HTML, so let’s start with a simple HTML page. The file tutor0.html, shown in Example 16-2, defines a bona fide, fully functional web page—a text file containing HTML code, which specifies the structure and contents of a simple web page.

Example 16-2. PP3E\Internet\Web\tutor0.html

<HTML>
<TITLE>HTML 101</TITLE>
<BODY>
<H1>A First HTML page</H1>
<P>Hello, HTML World!</P>
</BODY></HTML>

If you point your favorite web browser to the Internet address of this file, you should see a page like that shown in Figure 16-2. This figure shows the Firefox browser at work on the address http://localhost/tutor0.html (type this into your browser’s address field), and it assumes that the local web browser described ...