Question

I’m using Django for our project. And I have created a form using Django forms. In one of the form i need to check a variable and based on the value of the variable i need to add or remove an element.

I’m passing this variable to the form when the object is initialized.
ie form=MyForm(flag)

And in the forms class i’m doing this

class MyInfoForm(forms.Form):
    def __init__(self, *args,**kwargs):
        self.flag= kwargs.pop('flag', None)
        super(MyInfoForm, self).__init__(*args, **kwargs)
        print self.flag

    Firstname = forms.CharField(label=u' First name :', max_length=30)

In the init function i have printed the flag and its working fine. But how can i access the variable out side init
I tried

    class MyInfoForm(forms.Form):
        myFlag=None
        def __init__(self, *args,**kwargs):
            self.flag= kwargs.pop('flag', None)
            myFlag=self.flag
            super(MyInfoForm, self).__init__(*args, **kwargs)
            print self.flag

        Firstname = forms.CharField(label=u' First name :', max_length=30)
        print myFlag

But its not working.

Answer 1

The class statement is an executable statement that:

1. creates a namespaces
2. execute, sequentially, all code at the top-level of the class statement block
3. call the appropriate metaclass (defaulting to type) with the classname, namespace, and list of parent classes
4. bind the newly created class object to the classname in the enclosing (usually the module) namespace

To make a long story short you just cannot access instance attributes from within the class statement body, since neither the instance nor even the class itself exist yet.

If what you want is to update / add / remove fields on a per instance basis and according to some argument passed to the form’s initializer, the correct solution is to first call the parent’s initializer (to make sure your form’s instance fields are correctly initialized) then do whatever you have to do, ie:

class MyInfoForm(forms.Form):
    firstname = forms.CharField(label=u' First name :', max_length=30)
    def __init__(self, *args,**kwargs):
        self.flag= kwargs.pop('flag', None)
        super(MyInfoForm, self).__init__(*args, **kwargs)
        if self.flag:
            # XXX IMPORTANT : 
            # you want to access self.fields['fieldname']                
            # NOT self.fieldname
            self.fields["firstname"].label = "Yadda"