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lists to add just methods and operators related to set processing. Because all otherbehavior is inherited from the built-in list superclass, this makes for a shorter andsimpler alternative:class Set(list):def _ _init_ _(self, value = []):list._ _init_ _([])self.concat(value)def intersect(self, other):res = []for x in self:if x in other:res.append(x)return Set(res)def union(self, other):res = Set(self)res.concat(other)return resdef concat(self, value):for x in value:if not x in self:self.append(x)# Constructor# Customizes list# Copies mutable defaults# other is any sequence# self is the subject# Pick common items# Return a new Set# other is any sequence# Copy me and my list# value: list, Set...# Removes duplicatesdef _ _and_ _(self, other): return self.intersect(other)def _ _or_ _(self, other): return self.union(other)def _ _repr_ _(self): return 'Set:' + list._ _repr_ _(self)if _ _name_ _ == '_ _main_ _':x = Set([1,3,5,7])y = Set([2,1,4,5,6])print x, y, len(x)print x.intersect(y), y.union(x)print x & y, x | yx.reverse( ); print xHere is the output of the self-test code at the end of this file. Because subclassingcore types is an advanced feature, I’ll omit further details here, but I invite you totrace through these results in the code to study its behavior:% python setsubclass.pySet:[1, 3, 5, 7] Set:[2, 1, 4, 5, 6] 4Set:[1, 5] Set:[2, 1, 4, 5, 6, 3, 7]Set:[1, 5] Set:[1, 3, 5, 7, 2, 4, 6]Set:[7, 5, 3, 1]There are more efficient ways to implement sets with dictionaries in Python, whichreplace the linear scans in the set implementations shown here with dictionary indexoperations (hashing), and so run much quicker. (For more details, see ProgrammingPython.) If you’re interested in sets, also take another look at the set object type we542 | Chapter 26: Advanced Class Topics