How do I raise a ValidationError (or do something similar) in views.py of my Django?
I think gruszczy's answer is a good one, but if you're after generic validation involving variables that you think are only available in the view, here's an alternative: pass in the vars as arguments to the form and deal with them in the form's main clean() method.
The difference/advantage here is that your view stays simpler and all things related to the form content being acceptable happen in the form.
eg:
# IN YOUR VIEW # pass request.user as a keyword argument to the formmyform = MyForm(user=request.user)# IN YOUR forms.py# at the top:from myapp.foo.bar import ok_to_post # some abstracted utility you write to rate-limit posting # and in your particular Form definitionclass MyForm(forms.Form) ... your fields here ... def __init__(self, *args, **kwargs): self.user = kwargs.pop('user') # cache the user object you pass in super(MyForm, self).__init__(*args, **kwargs) # and carry on to init the form def clean(self): # test the rate limit by passing in the cached user object if not ok_to_post(self.user): # use your throttling utility here raise forms.ValidationError("You cannot post more than once every x minutes") return self.cleaned_data # never forget this! ;o)Note that raising a generic ValidationError in the clean() method will put the error into myform.non_field_errors so you'll have to make sure that your template contains {{form.non_field_errors}} if you're manually displaying your form
You don't use ValidationError in views, as those exceptions as for forms. Rather, you should redirect the user to some other url, that will explain to him, that he cannot post again that soon. This is the proper way to handle this stuff. ValidationError should be raised inside a Form instance, when input data doesn't validate. This is not the case.
You can use messages in views:
from django.contrib import messagesmessages.error(request, "Error!")Documentation: https://docs.djangoproject.com/es/1.9/ref/contrib/messages/