[Django]-Abstract form or form composition in django?

Multiple Inheritance won’t do what you want, if they all implement clean(), only the first mixin clean() will be called. How about simple polymorphism?

class RideForm(RideConditionPartForm):

    def clean():
        super clean()
        #other stuff

class RideConditionPartForm(RideGeographyPartForm):
   def clean():
     super clean()
     #other stuff