Is Python a

the instance’s memory address by calling the built-in id function, which returns anyobject’s address (by definition, a unique object identifier):############################################ Lister can be mixed into any class to# provide a formatted print of instances# via inheritance of _ _repr_ _ coded here;# self is the instance of the lowest class.###########################################class Lister:def _ _repr_ _(self):return ("" %(self.__class__._ _name_ _, # My class's nameid(self),# My addressself.attrnames( )) )# name=value listdef attrnames(self):result = ''for attr in self._ _dict_ _.keys( ):# Instance namespace dictif attr[:2] == '_ _':result = result + "\tname %s=\n" % attrelse:result = result + "\tname %s=%s\n" % (attr, self._ _dict_ _ [attr])return resultInstances derived from this class display their attributes automatically when printed,giving a bit more information than a simple address:>>> from mytools import Lister>>> class Spam(Lister):... def _ _init_ _(self):... self.data1 = 'food'...>>> x = Spam( )>>> xThe Lister class is useful for any classes you write—even classes that already have asuperclass. This is where multiple inheritance comes in handy: by adding Lister tothe list of superclasses in a class header (mixing it in), you get its _ _repr_ _ for freewhile still inheriting from the existing superclass. The file testmixin.py demonstrates:from mytools import Lister# Get tool classclass Super:def __init__(self):self.data1 = "spam"class Sub(Super, Lister):def _ _init_ _(self):Super._ _init_ _(self)self.data2 = "eggs"self.data3 = 42# superclass _ _init_ _# Mix in a _ _repr_ _# Lister has access to self# More instance attrs530 | Chapter 25: Designing with Classes