python class demo

#quote from 'introduction to computation and programming using python, revised edition, MIT'
class IntSet(object):
    """An intSet is a set of integers"""
    #Information about the implementation (not the abstraction)
    #The value of the set is represented by a list of ints, self.vals.
    #Each int in the set occurs in self.vals exactly once.
    
    def __init__(self):
        """Create an empty set of integers"""
        self.vals = []
        
    def insert(self, e):
        """Assumes e is an integer and serts e into self"""
        if not e in self.vals:
            self.vals.append(e)
            
    def member(self, e):
        """Assumes e is an integer
           Returns True if e is in self, and False otherwise"""
        return e in self.vals
        
    def remove(self, e):
        """Assumes e is an integer and removes e from self
           Raised ValueError if e is not in self"""
        try:
            self.vals.remove(e)
        except:
            raise ValueError(str(e) + ' not found')
            
    def getMembers(self):
        """Returns a s list containing the elements of self.
           Nothing can be assumed about the order of the elements"""
        return self.vals[:]
        
    def __str__(self):
        """Returns a string representation of self"""
        self.vals.sort()
        result = ''
        for e in self.vals:
            result = result + str(e) + ','
        return '{' + result[:-1] + '}' #-1 omits trailing comma