python - Where attribute does not exist, create an attribute and give it a default value -

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i learning python out of book , have written myself long quiz/type game prints summary @ end. however, summary looks attributes not exist depending on choices have been made user.

i have abstracted basic example show trying do. essentially, want run attribute error check, every variable not have attribute, create attribute default value of n/a.

in below example, want print:

forename: joe surname: bloggs smith test: n/a test 4: n/a

i created class called codecleaner going use set n/a values, got stuck!

class questionset(object):     next_set = 'first_set'  class claimengine(questionset):      def current_set(self):         last_set = "blank"         while_count = int(0)         quizset = sets.subsets         parentset = questionset()         while parentset.next_set != last_set , int(while_count)<50:             quizset[parentset.next_set].questioning()             while_count = while_count+1  class firstset(questionset):      def questioning(self):         self.value1 = raw_input("forename:\n")         questionset.next_set = "second_set"  class secondset(questionset):      def questioning(self):         self.value2 = raw_input("surname:\n")         if self.value2 == "smith":             self.value3 = "he's smith!"             self.value4 = "test val 4"             questionset.next_set = "summary"         else:              questionset.next_set = "summary"  class codecleaner(questionset):      def questioning(self):         mapping = sets()          sets = mapping.subsets         variable_list = {         [sets['first_set']].value1,         [sets['second_set']].value2,         [sets['second_set']].value3,         [sets['second_set']].value4         }         #while key_no < 4:         #   try:         #       print variable_list         #   except attributeerror:   class summary(questionset):      def questioning(self):         mapping = sets()          sets = mapping.subsets         print "forename:",sets['first_set'].value1         print "surname:",sets['second_set'].value2         print "smith test:",sets['second_set'].value3         print "test 4:",sets['second_set'].value4         exit(0)  class sets(object):         subsets = {         'first_set': firstset(),         'second_set': secondset(),         'summary': summary()         }  run = claimengine() run.current_set()

i feel quite lazy asking question, however, i've been wrestling few days now! appreciated.

i'm not sure go approach, can implement __getattr__ method in object called when attribute not found:

class a(object):     def __getattr__(self, name):         print("creating attribute %s."%name)         setattr(self, name, 'n/a')

then:

>>> = a() >>> a.a creating attribute a. >>> a.a 'n/a'

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