Programming Python, Second Edition

Sending Files to Clients and Servers

It’s time to explain a bit of HTML code we’ve been keeping in the shadows. Did you notice those hyperlinks on the language selector example’s main page for showing the CGI script’s source code? Normally, we can’t see such script source code, because accessing a CGI script makes it execute (we can see only its HTML output, generated to make the new page). The script in Example 12-23, referenced by a hyperlink in the main language.html page, works around that by opening the source file and sending its text as part of the HTML response. The text is marked with <PRE> as pre-formatted text, and escaped for transmission inside HTML with cgi.escape.

Example 12-23. PP2E\Internet\Cgi-Web\Basics\languages-src.cgi

#!/usr/bin/python
#################################################################
# Display languages.cgi script code without running it.
#################################################################

import cgi
filename = 'languages.cgi'

print "Content-type: text/html\n"       # wrap up in html
print "<TITLE>Languages</TITLE>"
print "<H1>Source code: '%s'</H1>" % filename
print '<HR><PRE>' 
print cgi.escape(open(filename).read(  ))
print '</PRE><HR>'

When we visit this script on the Web via the hyperlink or a manually typed URL, the script delivers a response to the client that includes the text of the CGI script source file. It appears as in Figure 12-25.

Figure 12-25. Source code viewer page

Note that here, too, it’s crucial to format the text ...