Core Python Programming (2nd Edition)

172 self.langs.append(eachLang.value)
173 else:
174 self.langs.append(langdata.value)
175 else:
176 self.error = 'At least one language required.'
177
178 if form.has_key('upfile'):
179 upfile = form["upfile"]
180 self.fn = upfile.filename or ''
181 if upfile.file:
182 self.fp = upfile.file
183 else:
184 self.fp = StringIO('(no data)')
185 else:
186 self.fp = StringIO('(no file)')
187 self.fn = ''
188
189 if not self.error:
190 self.doResults()
191 else:
192 self.showError()
193
194 if __name__ == '__main__':
195 page = AdvCGI()
196 page.go()
advcgi.py looks strikingly similar to our friends3.py CGI scripts seen earlier in this chapter. It has a
form, results, and error pages to return. In addition to all of the advanced CGI features that are part of
our new script, we are also using more of an object-oriented feel to our script by using a class with
methods instead of just a set of functions. The HTML text for our pages is now static data for our class,
meaning that they will remain constant across all instanceseven though there is actually only one
instance in our case.
Line-by-Line (Block-by-Block) Explanation
Lines 17
The usual startup and import lines appear here. The only module you may not be familiar with is
cStringIO, which we briefly introduced at the end of Chapter 10 and also used in Example 20.1.
cStringIO.StringIO() creates a file-like object out of a string so that access to the string is similar to
opening a file and using the handle to access the data.
Lines 912
After the AdvCGI class is declared, the header and url (static class) variables are created for use by the
methods displaying all the different pages.
Lines 1480
All the code in this block is used to generate and display the form page. The data attributes speak for
themselves. getCPPCookies() obtains cookie information sent by the Web client, and showForm() collates