class PhoneNumber:
    """
    A PhoneNumber represents a single phone number made up of the area code,
    exchange, and the line number.

    EX: (415) 552-7909
          ^    ^   ^
          |    |   |
          |    |   number
          |    exchange
          area code
    """
    def __init__(self, area_code, exchange, number):
        """
        Creates a new PhoneNumber from the provided area code, exchange and
        number.
        """
        self.area_code = area_code
        self.exchange = exchange
        self.number = number

    def call(self):
        """
        Calls this PhoneNumber.
        """
        print "Calling (" + str(self.area_code) + ") " + str(self.exchange) \
            + "-" + str(self.number)
        print "ring... ring... Hello?"

    def print_number(self):
        """
        Prints a pretty version of this PhoneNumber.
        """
        print "(" + str(self.area_code) + ") " + str(self.exchange) \
            + "-" + str(self.number)

class PhoneBook:
    """
    A PhoneBook is a collection of names and phone numbers.
    """
    def __init__(self):
        """
        Creates a new PhoneBook that is initially empty.
        """
        self.contacts = {}

    def add_number(self, name, phone_number):
        """
        Adds the provided name and PhoneNumber to this PhoneBook. Will replace
        the number if the name already exists in this PhoneBook.
        """
        self.contacts[name] = phone_number

    def delete_contact(self, name):
        """
        Removes the provided name and the associated PhoneNumber from this
        PhoneBook.
        """
        # This is how to remove from a dict. We might not have used this before.
        del self.contacts[name]

    def call(self, name):
        """
        Calls the phone number associated with the provided name.
        """
        self.contacts[name].call()
        print "Hi this is " + name + "."

    def get_phone_number(self, name):
        """
        Returns the PhoneNumber associated with the provided name.
        """
        return self.contacts[name]

    def get_contacts_in_area_code(self, area_code):
        """
        Returns a list of all PhoneNumbers in this PhoneBook that have
        the given area_code.
        """
        result = []
        for name in self.contacts:
            num = self.contacts[name]
            if num.area_code == area_code:
                result.append(num)

        return result