Event Handlers

Event handlers are callable functions bound to an event that, at a minimum, get passed a single parameter, event, which is an Event instance. All Event instances come with at least three attributes:

• Event.assoc - the Association in which the event occurred

• Event.event - the corresponding event, as a Python namedtuple

• Event.timestamp - the date and time the event occurred at, as a Python datetime.datetime

Additional attributes and properties are available depending on the event type, see the handler implementation documentation for more information.

Handlers can be bound to events through the evt_handlers keyword parameter with AE.associate() and AE.start_server(). evt_handlers should be a list of 2- or 3-tuples:

from pynetdicom import evt, AE
from pynetdicom.sop_class import Verification, CTImageStorage

def handle_echo(event):
    # Because we used a 2-tuple to bind `handle_echo` we
    #   have no extra parameters
    return 0x0000

def handle_store(event, arg1, arg2):
    # Because we used a 3-tuple to bind `handle_store` we
    #   have optional extra parameters
    assert arg1 == 'optional'
    assert arg2 == 'parameters'
    return 0x0000

handlers = [
    (evt.EVT_C_ECHO, handle_echo),
    (evt.EVT_C_STORE, handle_store, ['optional', 'parameters']),
]

ae = AE()
ae.add_supported_context(Verification)
ae.add_supported_context(CTImageStorage)
ae.start_server(("127.0.0.1", 11112), evt_handlers=handlers)

If using a 3-tuple then the third item should be a list of objects that will be passed to the handler as extra parameters.

The other way to bind handlers to events is through the Association.bind() and AssociationServer.bind() methods. Handlers can be unbound with Association.unbind() and AssociationServer.unbind() methods. See the Association guide for more details.