Inheritance and init method in Python

Question

I m begginer of python  I can t understand inheritance and   init       class Num      def   init   self num           self n1   num  class Num2 Num       def show self           print self n1  mynumber   Num2 8  mynumber show     RESULT  8  This is OK  But I replace Num2 with  class Num2 Num       def   init   self num           self n2   num 2     def show self           print self n1 self n2   RESULT  Error  Num2 has no attribute  n1    In this case  how can Num2 access n1

User · Answer

Since you don t call Num   init     the field  n1  never gets created  Call it and then it will be there

User · Answer

A simple change in Num2 class like this  super     init   num    It works in python3  class Num          def   init   self num                   self n1   num  class Num2 Num           def   init   self num                   super     init   num                  self n2   num 2         def show self                   print  self n1 self n2   mynumber   Num2 8  mynumber show

User · Answer

In the first situation  Num2 is extending the class Num and since you are not redefining the special method named   init     in Num2  it gets inherited from Num      When a class defines an   init       method  class instantiation   automatically invokes   init     for   the newly-created class instance    In the second situation  since you are redefining   init     in Num2 you need to explicitly call the one in the super class  Num  if you want to extend its behavior   class Num2 Num       def   init   self num           Num   init   self num          self n2   num 2

User · Answer

When you override the init you have also to call the init of the parent class  super Num2  self    init   num    Understanding Python super   with   init     methods

[python] Inheritance and init method in Python

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