Inconsistency in CGI Documentation????
rnd at onego.ru
Tue Aug 21 18:42:18 CEST 2001
On Tue, 21 Aug 2001, Maan M. Hamze wrote:
>While working on a Python CGI script I ran into the following:
>Assume I have a form with a Text Input element. The element has a name, but
>I chose not to set its value, or to set value to "" (empty).
>I import CGI module and define: Test_Form = cgi.FieldStorage()
>1. PythonWin documentation of Python states the following:
>Form fields containing empty strings are ignored and do not appear in the
>dictionary; to keep such values, provide the optional "keep_blank_values"
>argument when creating the FieldStorage instance.
>Question: How do you provide this argument?
>Test_Form=cgi.FieldStorage(keep_blank_values)?? This is not working.
OK. Trying this:
>>> import os
>>> Test_Form = cgi.FieldStorage()
>>> Test_Form = cgi.FieldStorage(keep_blank_values=1)
['aaa', 'b', 'c']
I can't see any inconsitencies...
nb. the way keep_blank_values are given (it's a named argument).
>Ok! I am not going to provide this argument. So, the Text Input element
>that I left empty and had not provided a vlaue for should NOT make it into
>FieldStorage() if user does not type some characters in it. Right? I tried
>it. It does not make it.
>Even if I provide a value of " " (is " " an empty string??)
>2. BUT, read on:
>check http://www.python.org/doc/essays/ppt/sd99east/sld041.htm Slide # 40
><form method="POST" action="http://host.com/cgi-bin/test.py">
>Your first name: <input type="text" name="firstname">
><submit button goes here>
><input type="hidden" name="session" value="1f9a2">
>Ok! So here it is, a Text Input element with no value. From the
>documentation above in 1., this element should not be in FieldStorage unless
>one types in something.
>Now, move into Slide 41:
> print "Content-type: text/html\n"
> form = cgi.FieldStorage() # parse query
> if form.has_key("firstname") and form["firstname"].value != "":
> print "Hello", form["firstname"].value
> print "Error! Please enter first name."
>Of interest is: if form.has_key("firstname") and form["firstname"].value
>How come we are checking for the key AND that the vlaue of the key is not
>""? Is not that code assuming that a non-empty string can be included in
Good programs are not relying on such a subtlety as default
>FieldStorage() without using keep_blank_values? Thus a contradiction with
>what point 1. has to say about it?
>I am really trying to understand this. Can someone help?
Sincerely yours, Roman Suzi
_/ Russia _/ Karelia _/ Petrozavodsk _/ rnd at onego.ru _/
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