Question

This looks really ugly, it there a way to make it look more pythonic?

if self.cleaned_data['string1_val'] == '' and latestSI.string1_val is None :
    if self.cleaned_data['string2_val'] == '' and latestSI.string2_val is None :
        return False
    elif self.cleaned_data['string2_val'] == latestSI.string2_val :
        return False
    else:
        return True
elif self.cleaned_data['string1_val'] == latestSI.string1_val :
    if self.cleaned_data['string2_val'] == '' and latestSI.string2_val is None :
        return False
    elif self.cleaned_data['string2_val'] == latestSI.string2_val :
        return False
    else:
        return True
else:
    return True

Answer 1

All your issues stem from Nones. Clean them up and your logic becomes trivial.

cd1 = self.cleaned_data['string1_val']
lsi1 = latestSI.string1_val
cd2 = self.cleaned_data['string2_val']
lsi2 = latestSI.string2_val
if lsi1 is None:
  lsi1 = ''
if lsi2 is None:
  lsi2 = ''
return not (cd1 == lsi1 and cd2 == lsi2)