Class constants in python

Question

In python  I want a class to have some  quot constants quot   practically  variables  which will be common in all subclasses  Is there a way to do it with friendly syntax  Right now I use  class Animal      SIZES   quot Huge quot   quot Big quot   quot Medium quot   quot Small quot    class Horse Animal       def printSize self           print Animal SIZES 1    and I m wondering if there is a better way to do it or a way to do it without then having to write  quot Animal  quot  before the sizes  Horse inherits from Animal

User · Answer

Expanding on betabandido s answer  you could write a function to inject the attributes as constants into the module   def module register class constants klass  attr prefix       globals   update           name  getattr klass  name   for name in dir klass  if name startswith attr prefix         class Animal object       SIZE HUGE    Huge      SIZE BIG    Big   module register class constants Animal   SIZE     class Horse Animal       def printSize self           print SIZE BIG

User · Answer

class Animal      HUGE    Huge      BIG    Big   class Horse      def printSize self           print Animal HUGE

User · Answer

Since Horse is a subclass of Animal  you can just change  print Animal SIZES 1     with  print self SIZES 1     Still  you need to remember that SIZES 1  means  big   so probably you could improve your code by doing something like   class Animal      SIZE HUGE  Huge      SIZE BIG  Big      SIZE MEDIUM  Medium      SIZE SMALL  Small   class Horse Animal       def printSize self           print self SIZE BIG    Alternatively  you could create intermediate classes  HugeAnimal  BigAnimal  and so on  That would be especially helpful if each animal class will contain different logic

User · Answer

You can get to SIZES by means of self SIZES  in an instance method  or cls SIZES  in a class method    In any case  you will have to be explicit about where to find SIZES  An alternative is to put SIZES in the module containing the classes  but then you need to define all classes in a single module

[python] Class constants in python

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