Creates derivative of (base) word by adding any affixes that apply

def create_derivative(self, word):
        ''' Creates derivative of (base) word by adding any affixes that apply '''
        result = None
        if self.char_to_strip != '':
            if self.opt == "PFX":
                result = word[len(self.char_to_strip):len(word)]
                result = self.affix + result 
            else: # SFX
                result = word[0:len(word) - len(self.char_to_strip)]
                result = result + self.affix
        else: # No characters to strip
            if self.opt == "PFX":
                result = self.affix + word
            else: # SFX
                result = word + self.affix

        # None means word does not meet the set condition
        return result