[Tutor] cgi.FieldStorage and dictionary.get(' ')

[Patric Michael]

Forwarded to the list...

> On Thu, 30 Dec 2004 22:58:14 -0800, Patric Michael <patric at usa.net>
> wrote: > > First off, make sure that you have the "Content-Type:
> text/html\n\n" > line print before anything else whenever you send
> output to the web. > Presumably it worked for the form display, but
> you have to keep resending it      > each time the page changes. > >
> Without seeing the def for login(failure), and not being familiar with
> SQL, I'll take > a pass on these lines, but I am curious why you
> declare failure as true or false in > the login function? > > Instead
> of form.get(), try this: > >          print form['author'].value >    
>      print form['password'].value > 
> 
> Hi,
> 
> def main(form):
>    if form.has_key('author') and form.has_key('password'):
>       author = form['author'].value
>       password = form['password'].value
>       q = Users.select(AND(Users.q.author==author,
>                            Users.q.password==password))
>       if len(list(q))>0:
>          chapters(author)
>       else:
>          login(failure=True)
>    else:
>       login(failure=False)
> 
> Using form['author'].value works so long as it's assigned to a
> variable before being looked up by sqlobject. This is interesting
> because, if I try this from the interperter:
> 
> >>> author = form['author'].value
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> AttributeError: 'str' object has no attribute 'value'

Right.  If I recall correctly, the .value method is specific to the cgi 
module since FieldStorage() is actually a bunch of dictionaries 
contained in a list.  
The .value method shortcuts the need to extract the dictionary from the 
list, then extract the key/value pair from the result and lets you grab the 
value directly.  (Someone correct me if I misremember this, please!)

> 
> I define login(failure) as True or False because the first time the
> user reaches the login page they shouldn't be presented with a failure
> message. The second time round they should.

Oh cool.  I hadnt thought of that.  I usually use a try: statement to test 
for one of the keys to determine whether the script sends the initial login 
form, or the login form with appropriate error messages prepended.  
That way I can explicitly indicate which field(s) need attention.
> 
> Everything happens through a driver script:
> 
> #!/usr/local/bin/python
> 
> print 'Content-type: text/html\n\n'
> 
> import cgi
> from spanishlabs.gui import *
> 
> if __name__ == '__main__':
>    main(form=cgi.FieldStorage())
> 
> Thanks for your help!
> 

No problem!

Patric