Set.py

class Set:
    # Creates an empty set instance
    def __init__( self ):
        self._theElements = list()

    # Returns the number of items in the set.
    def __len__( self ):
        return len( self._theElements )
    
    # Determines if an element is in the set.
    def __contains__( self, element ):
        return element in self._theElements
    
    # Adds a new unique element to the set.
    def add( self, element ):
        if element not in self :
            self._theElements.append( element )
    
    # Removes an element from the set.
    def remove( self, element ):
        assert element in self,"The element must be in the set."
        self._theElements.remove( item )
    
    # Determines if two sets are equal.
    def __eq__( self, setB ):
        if len( self ) != len( setB ) :
            return False
        else:
            return self.isSubsetOf( setB )

    def isSubsetOf( self, setB ):
        for element in self :
            if element not in setB :
                return False
            return True
    
    # Creates a new set from the union of this set and setB.
    def union( self, setB ):
        newSet = Set()
        newSet._theElements.extend( self._theElements )
        for element in setB :
            if element not in self :
                newSet._theElements.append( element )
                return newSet
    
    # Creates a new set from the intersection: self set and setB.
    # def interset( self, setB ):
        
    # Creates a new set from the difference: self set and setB.
    # def difference( self, setB ):
    
    # Returns an iterator for traversing the list of items.
    def __iter__( self ):
        return _SetIterator( self._theElements )

class _SetIterator:
    for i in range(len(Set())):
        print(Set())