dictionary - python dict() initialisation -

since few weeks learning python. have background in c++, might explain question.

it following python code:

#!/usr/bin/python2 # -*- coding: utf-8 -*-   class testa:     dictionary = dict()      def __init__(self):         pass   class testb:     dictionary = none      def __init__(self):         self.dictionary = dict()   def main():     ta1 = testa()     ta2 = testa()     tb1 = testb()     tb2 = testb()      ta1.dictionary["test1"] = 1     ta1.dictionary["test2"] = 2     ta2.dictionary["test3"] = 3     ta2.dictionary["test4"] = 4      print "testa ta1"     key in ta1.dictionary.keys():         print "  " + key + "\t" + str(ta1.dictionary[key])     print "testa ta2"     key in ta2.dictionary.keys():         print "  " + key + "\t" + str(ta2.dictionary[key])       tb1.dictionary["test1"] = 1     tb1.dictionary["test2"] = 2     tb2.dictionary["test3"] = 3     tb2.dictionary["test4"] = 4      print "testb tb1"     key in tb1.dictionary.keys():         print "  " + key + "\t" + str(tb1.dictionary[key])     print "testb tb2"     key in tb2.dictionary.keys():         print "  " + key + "\t" + str(tb2.dictionary[key])  if __name__ == '__main__':     main() 

the output of code is:

$ python2 pytest.py  testa ta1   test1 1   test3 3   test2 2   test4 4 testa ta2   test1 1   test3 3   test2 2   test4 4 testb tb1   test1 1   test2 2 testb tb2   test3 3   test4 4 

however, not understand why dictionaries in ta1 , ta2 same. reason behaviour?

the dictionary attribute of testa belongs class , not instances. reason why instances of testa same. should this:

class testa:     def __init__(self):         self.dictionary = dict() # make dictionary belong instance, , each instance own copy of dictionary