Why can not initialize the class?

[Larry Martell]

On Fri, Aug 22, 2014 at 10:58 AM, luofeiyu <elearn2014 at gmail.com> wrote:
>>>> class Contact(object):
> ...     def __init__(self, first_name=None, last_name=None,
> ...                  display_name=None, email="haha at haha"):
> ...         self.first_name = first_name
> ...         self.last_name = last_name
> ...         self.display_name = display_name
> ...         self.email = email
> ...     def print_info(self):
> ...         print(self.display_name, "<" + self.email + ">"  )
> ...     def set_email(self, value):
> ...         print(value)
> ...         self._email = value
> ...     def get_email(self):
> ...         return self._email
> ...     email = property(get_email, set_email)
> ...
>>>>
>>>> contact = Contact()
> haha at haha
>
> why the value in `def set_email(self, value): `  is  haha at haha?
> how haha at haha  is called to  value in `def set_email(self, value): `?
> would you mind telling me the process?

https://docs.python.org/3.4/library/functions.html#property