Programming Python, 3rd Edition

Transferring 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 16-26, 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 preformatted text, and is escaped for transmission inside HTML with cgi.escape.

Example 16-26. PP3E\Internet\Web\cgi-bin\languages-src.py

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

import cgi
filename = 'cgi-bin/languages.py'

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>'

Here again, the filename is relative to the server’s directory for our web server on Windows (see the prior note, and delete the cgi-bin portion of its path on other platforms). When we visit this script on the Web via the hyperlink or a manually typed URL, the script delivers a response ...