How to store contacts that has been added, so that they can be checked for duplicate contacts already stored?

class Phonebook:
    def addContact (self):


        name=str(input('enter name:'))
        lastname=str(input('enter lastname:'))
        number=int(input('enter number:'))

        contact_type=int(input('enter 1 for business contact and 2 for personal contact'))

        if contact_type==1: #add business contact
            company=str(input('enter company:'))
            businessAdress=str(input('enter businessAdress:'))
            #adding a contacts value:
            name=BusinessContact(name,lastname,number,company,businessAdress)

        elif contact_type==2:
            homeAdress=str(input('enter Homeadress'))
            relation=str(input('enter relation'))
            #adding a contacts value:
            name=BusinessContact(name,lastname,number,homeAdress,relation)   

        print('contact entered:')
        print(name.__dict__)

class Contact:
    def __init__ (self,name,surname,phone):
        self.name=name
        self.surname=surname
        self.phone=phone

class BusinessContact (Contact): #subclass. business contact are a contact.
    def __init__ (self,name,surname,phone,company,businessAdress):
        Contact.__init__(self,name,surname,phone)
        self.company=company
        self.businessAdress=businessAdress

class PersonalContact (Contact): #subclass.
    def __init__(self,name,surname,homeadress,realationship):
        Contact.__init__(self,name,surname,phone)
        self.homeadress=homeadress
        self.relationship=relationship


s=Phonebook()
s.addContact()