calculated form field

[bolivar4]

Want to present users a form in which numbers are entered, then manipulated in a view and a calculated value is returned to the screen.

After looking in the the Django book around the net this is what I have come, (it doesn't work) shows below.  So far, the three fields setup in forms.py render to the secreen, that is all I'm getting.

I am getting this error in the django 404 exception page: "unsupported operand type(s) for *: 'NoneType' and 'NoneType'"

 

It is purposely a  simple exercise, more interested  in technique of doing this so, I know this can be done in javascript, but I want to do this with python/django.

Thank you to anyone who can help me out, this has been a problem all weekend.

 

forms.py:

 

from django import forms

 

class FinanceTable(forms.Form):

       capital = forms.IntegerField(required=False)

       tax_rate = forms.DecimalField(required=False)

       useage = forms.IntegerField(required=False)

 

views.py:

 

from django.shortcuts import render_to_response

 

def  calculation(request):

       """view that sets up form calculation"""

       if request.method == 'POST':

            form  = FinanceTable(request.POST)

            if form.is_valid():

                 capital = form.cleaned_data['capital']

                  tax_rate = form.cleaned_data['tax_rate']

                  useage = form.cleaned_data['capital'] * form.cleaned_data['tax_rate']                 

                  response_dict = {'capital' : capital, 'tax_rate'  : tax_rate, 'useage' : useage}

                  return render_to_response('focus_areas.html', response_dict)

        else:

              form = FinanceTable(

                             initial={'capital' : 1000, tax_rate : .07}

               )

        return render_to_response('focus_areas.html', {'form' : form}) 

 

 

html in template:

          <form action="" method= "" method="post">

                  <table>

                          {{ form.as_table }}

                  </table>

                  <input type="submit" value = "Submit"/>

          </form>

 

 

Any help ios much appreciated.

 

 

 

 

 

 

 

 

 

 

              

[Joel Goldstick]

What does your urls.py file look like. If you are getting 404 then it
may not be finding your view.
--
Joel Goldstick

[Tim Ney]

Thank you for responding, this is a vexing problem.

I know the urs.py is fine, as the the form html code I posted

is part of an .html, largely static html, which renders to the screen fine.

The form fields are also showing up in the rendered page, and numbers can be

entered, when the submit button is clicked I get the exception

Did I not understand your question, I am new at this.

 

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[Rajeesh Nair]

Your FormClass expects all 3 fields to be optional (required=False). But your code in view always expects them to have integer values. And you end up multiplying values from two blank fields! Either you provide some default value to the fields or rewrite view to use form.cleaned_data.get with a default value as 2nd argument to it.

On Monday, March 19, 2012 9:11:27 PM UTC+5:30, bolivar4 wrote:

"unsupported operand type(s) for *: 'NoneType' and 'NoneType'"

 

[Tim Ney]

Rajeesh,

 

Following your advice, Im think I've about solved the problem.

I've got one last exception, I hope.

 

Here is the new iteration of views.py, all other files remain the same.

In short the page renders to the screen, the problem arises when values are submitted

to the view.

 

I get an exception  "can't multiply sequence by non-int of type 'tuple". I've created a new

function that describes the multiplication operation, that is used within the render function, this

is where the error occcrs. I'm not referencing the variables properly, I guess.

 

def calculation(request):

     """function that computes submission"""

    if request.method == 'POST':

         form = FinanceTable(request.POST)

         if form.is_valid():

           cd =form.cleaned_data

           capital = cd['capital'],

           tax_rate = cd['tax_rate'],

           useage = projfin(request, capital, tax_rate)

           response_dict = {'capital' : capital, 'tax_rate' : tax_rate, 'useage' : useage}

           return render_to_response('textplusnumbers.html' , response_dict)

   else:

         form = FinanceTable(

                      initial={'capital' : 1000, 'tax_rate' : .07}

                      )

 

   return render_to_response('textplusnumbers.html' , {'form' : form})

 

def projfin(request, capital, tax_rate):

     useage = capital * tax_rate

     return useage          

 

 

 

 

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[Babatunde Akinyanmi]

Why not just do:

useage = capital * tax_rate

Instead of your projfin function. In the projfin function, the request
you are passing is also redundant.

As for the error, I don't know how you refactored your models code but
obviously from the error message, you are not passing in ints. You can
try to debug the code by printing capital and tax_rate so you can see
what values are being passed into the function.

>> Your FormClass expects all 3 fields to be optional (*required=False*).

>> But your code in view always expects them to have integer values. And you
>> end up multiplying values from two blank fields! Either you provide some
>> default value to the fields or rewrite view to use

>> *form.cleaned_data.get*with a default value as 2nd argument to it.

>>
>>
>> On Monday, March 19, 2012 9:11:27 PM UTC+5:30, bolivar4 wrote:
>>
>>>
>>>
>>> "unsupported operand type(s) for *: 'NoneType' and 'NoneType'"
>>>
>>>
>>> class FinanceTable(forms.Form):

>>> capital = forms.IntegerField(required=**False)
>>> tax_rate = forms.DecimalField(required=**False)
>>> useage = forms.IntegerField(required=**False)

>>>
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[Tim Ney]

Thank you for your response.

 

1. The fact that I'm using a function and then referencing the function in the

        render should not make a difference.

2. I'm not using a database model.

3. Where is the redundancy?

4. When you respond to a request for help an example

      of how you would solve the problem whould help, that I is why

      I took the time to type in th the forms.py file, the views.py and the html.

5. You don't need to respond to this.