django - Argument of type 'NoneType' is not iterable when trying to update a model object -

getting error argument of type 'nonetype' not iterable , can't figure out why.

it happens @ line if model_form.is_valid():

views.py

def update_model(request, pricemodel_id):     """ update part given id. """     pricemod = part.objects.get(id=pricemodel_id)     if request.method == "post":         print "post request"         model_form = priceform(request.post, request.files, instance=pricemod)         model_form.is_update = true         if request.user == pricemod.adder:             #from ipdb import set_trace; set_trace()             if model_form.is_valid(): 

forms.py

class priceform(modelform): # price form: form associated part model     def __init__(self, *args, **kwargs):         super(priceform, self).__init__(*args,**kwargs)         self.is_update=false         choices = unipart.objects.all().values('manufacturer').distinct()     def clean(self):         if self.cleaned_data , 'modelname' not in self.cleaned_data:             raise forms.validationerror("some error message")             if not self.is_update:                 return self.cleaned_data             return self.cleaned_data     class meta:         model = part 

looks because wrong indention in clean method. current doesn't return anything, i.e returns none, must return self.cleaned_data. of clean method code under if, raise exception. , if if not matched, none returned.

try this:

class priceform(modelform):     # ...     def clean(self):         if self.cleaned_data , 'modelname' not in self.cleaned_data:             raise forms.validationerror("some error message")         if not self.is_update:             return self.cleaned_data         return self.cleaned_data      # ...