# The mailing list manager

The `IListManager` is how you create, delete, and retrieve mailing list objects.

    >>> from mailman.interfaces.listmanager import IListManager
    >>> from zope.component import getUtility
    >>> list_manager = getUtility(IListManager)

## Creating a mailing list

Creating the list returns the newly created IMailList object.

    >>> from mailman.interfaces.mailinglist import IMailingList
    >>> mlist = list_manager.create('test@example.com')
    >>> IMailingList.providedBy(mlist)
    True

All lists with identities have a short name, a host name, a fully qualified listname, and an RFC 2369 list id. This latter will not change even if the mailing list moves to a different host, so it is what uniquely distinguishes the mailing list to the system.

    >>> print(mlist.list_name)
    test
    >>> print(mlist.mail_host)
    example.com
    >>> print(mlist.fqdn_listname)
    test@example.com
    >>> print(mlist.list_id)
    test.example.com

## Deleting a mailing list

Use the list manager to delete a mailing list.

    >>> list_manager.delete(mlist)
    >>> sorted(list_manager.names)
    []

After deleting the list, you can create it again.

    >>> mlist = list_manager.create('test@example.com')
    >>> print(mlist.fqdn_listname)
    test@example.com

## Retrieving a mailing list

When a mailing list exists, you can ask the list manager for it and you will always get the same object back.

    >>> mlist_2 = list_manager.get('test@example.com')
    >>> mlist_2 is mlist
    True

You can also get a mailing list by it’s list id.

    >>> mlist_2 = list_manager.get_by_list_id('test.example.com')
    >>> mlist_2 is mlist
    True

If you try to get a list that doesn’t existing yet, you get `None`.

    >>> print(list_manager.get('test_2@example.com'))
    None
    >>> print(list_manager.get_by_list_id('test_2.example.com'))
    None

You also get `None` if the list name is invalid.

    >>> print(list_manager.get('foo'))
    None

## Iterating over all mailing lists

Once you’ve created a bunch of mailing lists, you can use the list manager to iterate over the mailing list objects, the list posting addresses, or the list address components.

    >>> mlist_3 = list_manager.create('test_3@example.com')
    >>> mlist_4 = list_manager.create('test_4@example.com')

    >>> for name in sorted(list_manager.names):
    ...     print(name)
    test@example.com
    test_3@example.com
    test_4@example.com

    >>> for list_id in sorted(list_manager.list_ids):
    ...     print(list_id)
    test.example.com
    test_3.example.com
    test_4.example.com

    >>> for fqdn_listname in sorted(m.fqdn_listname
    ...                             for m in list_manager.mailing_lists):
    ...     print(fqdn_listname)
    test@example.com
    test_3@example.com
    test_4@example.com

    >>> for list_name, mail_host in sorted(list_manager.name_components):
    ...     print(list_name, '@', mail_host)
    test   @ example.com
    test_3 @ example.com
    test_4 @ example.com