Easy define python constants type.

constants.py

class Constants(type):
  
    class _ConstantsBase(dict):
    
        def __getattribute__(self, name):
            try:
                return self[name]
            except LookupError:
                raise AttributeError(name)
        
        def __contains__(self, name):
            return name in dict.values(self)
    
    def __new__(mcs, name, bases, dct):        
        d = {}
        for k, v in dct.items():
            if not k.startswith("_"):
                d[k] = v
                
        return type(name, (Constants._ConstantsBase,), dct)(d)

    
class COLOR_TYPES(object):
    __metaclass__ = Constants
    
    RED = "red"
    GREEN = "green"
    BLUE = "blue"
    

if __name__ == "__main__":
    print COLOR_TYPES
    # >> {'BLUE': 'blue', 'GREEN': 'green', 'RED': 'red'}
    print COLOR_TYPES.RED
    # >> red
    print "red" in COLOR_TYPES
    # >> True
    print "yellow" in COLOR_TYPES
    # >> False

See also https://docs.python.org/3/library/enum.html