What is the best way to track model field changes through a form?

Question

Django

Hello. There is a user model MyUser. In the form UserInf I change I give the user the opportunity to change from 0 to all fields of the form and, accordingly, the model. How to keep track of which fields are changed and not overwrite unmodified fields with default empty strings?
At the moment there is the following view:

def profile_change(request):
    if request.method == 'GET':
        current_inf = MyUser.objects.get(id = request.user.id)
        form = UserInf()
        return render(request, 'profile_change.html', context={'edit_form':form,
        'user':current_inf})
    elif request.method == 'POST':
        form = UserInf(request.POST)
        if form.is_valid():
            current_password = request.user.password
            form_cleaned = form.cleaned_data
            if check_password(form_cleaned['old_password'],current_password):
                if form_cleaned['password'] == form_cleaned['password2']:
                    user = form.save(commit=False)
                    user.password = form_cleaned['password']
                    user.id = request.user.id
                    user.user = request.user
                    user.save()
                    id = request.user.id
                else:
                    pass
            else:
                pass
            user = MyUser.objects.get(id=request.user.id)
            # как отследить, какие поля формы заполнены?
            return HttpResponseRedirect(reverse('profile', kwargs={'id':id}))
        else:
            pass

And the form itself:

class UserInf(forms.ModelForm):
    old_password = forms.CharField(widget=forms.PasswordInput, label="Старый пароль", required=False)
    password = forms.CharField(widget=forms.PasswordInput, label="Введите пароль", required=False)
    password2 = forms.CharField(widget=forms.PasswordInput, label="Подтвердите пароль",required=False)

    class Meta:
        model = MyUser
        fields = ('photo','firstname','surname','patronym','country')
        labels = {'firstname':'Имя','surname':'Фамилия',
        'patronym':'Отчество','country':'Страна'}

Answer 1

You don't need to keep track of this, if you use ModelForm, then why don't you use instance, but do everything manually?