Add members to an Outlook distribution

add_dl_members.py

"""
    Add members to an existing user distribution list in Python
    
    https://docs.microsoft.com/en-us/office/vba/api/outlook.mailitem.recipients
    https://docs.microsoft.com/en-us/office/vba/api/outlook.distlistitem.addmembers
    https://docs.microsoft.com/en-us/office/vba/api/outlook.oldefaultfolders
"""
import win32com.client as client

# start an instance of outlook
outlook = client.Dispatch('Outlook.Application')

# get the namespace and default contacts folder (10)
namespace = outlook.GetNameSpace('MAPI')
contacts = namespace.GetDefaultFolder(10)

# get the distribution list by name from the contact items
distro = contacts.Items['MyTestDistro']

# create a temp mail item to hold recipients
temp_obj = outlook.CreateItem(0)
recipients = temp_obj.recipients

# add a few recipients to the recipients item
recipients.Add('person_1@outlook.com')
recipients.Add('person_2@outlook.com')
recipients.Add('person_3@outlook.com')

# resolve the address to match with any existing contacts
recipients.ResolveAll()

# add a members to distribution
distro.AddMembers(recipients)
distro.Save()