[Django]-Disconnect signals for models and reconnect in django

You can connect and disconnect signals as Haystack does in RealTimeSearchIndex, which seems more standard:

from django.db.models import signals
signals.pre_save.disconnect(pre_save_model, sender=MyModel)
a.save()
signals.pre_save.connect(pre_save_model, sender=MyModel)

I haven’t tested the following code, but it should work:

from django.db.models.signals import pre_save


def save_without_the_signals(instance, *args, **kwargs):
    receivers = pre_save.receivers
    pre_save.receivers = []
    new_instance = instance.save(*args, **kwargs)
    pre_save.receivers = receivers
    return new_instance

It will silence signals from all sender’s though not just instance.__class__.

This version disables only the given model’s signals:

from django.db.models.signals import pre_save
from django.dispatch.dispatcher import _make_id


def save_without_the_signals(instance, *args, **kwargs):
    receivers = []
    sender_id = _make_id(instance.__class__)
    for index in xrange(len(self.receivers)):
        if pre_save.receivers[index][0][1] == sender_id:
            receivers.append(pre_save.receivers.pop(index))
    new_instance = instance.save(*args, **kwargs)
    pre_save.receivers.extend(receivers)
    return new_instance

If you only want disconnect and reconnect one custom signal, you may use this code:

def disconnect_signal(signal, receiver, sender):
    disconnect = getattr(signal, 'disconnect')
    disconnect(receiver, sender)

def reconnect_signal(signal, receiver, sender):
    connect = getattr(signal, 'connect')
    connect(receiver, sender=sender)

In this way you can make this:

disconnect_signal(pre_save, pre_save_model, MyModel)
a.save()
reconnect_signal(pre_save, pre_save_model, MyModel)

I needed to prevent certain signals from firing during unittests so I made a decorator based on qris’s response:

from django.db.models import signals

def prevent_signal(signal_name, signal_fn, sender):
    def wrap(fn):
        def wrapped_fn(*args, **kwargs):
            signal = getattr(signals, signal_name)
            signal.disconnect(signal_fn, sender)
            fn(*args, **kwargs)
            signal.connect(signal_fn, sender)
        return wrapped_fn
    return wrap

Using it is simple:

@prevent_signal('post_save', my_signal, SenderClass)
def test_something_without_signal(self):
    # the signal will not fire inside this test

Here is solution to temporary disable signal receiver
per instance which allows to use it on production (thread-safe)

[usage.py]

from django.db.models.signals import post_save

payment = Payment()
with mute_signals_for(payment, signals=[post_save]):
   payment.save()  # handle_payment signal receiver will be skipped

[code.py]

from contextlib import contextmanager
from functools import wraps

MUTE_SIGNALS_ATTR = '_mute_signals'


def mutable_signal_receiver(func):
    """Decorator for signals to allow to skip them by setting attr MUTE_SIGNALS_ATTR on instance,
    which can be done via mute_signals_for"""
    @wraps(func)
    def wrapper(sender, instance, signal, **kwargs):
        mute_signals = getattr(instance, MUTE_SIGNALS_ATTR, False)
        if mute_signals is True:
            pass  # skip all signals
        elif isinstance(mute_signals, list) and signal in mute_signals:
            pass  # skip user requested signal
        else:  # allow signal receiver
            return func(sender=sender, instance=instance, signal=signal, **kwargs)
    return wrapper


@contextmanager
def mute_signals_for(instance, signals):
    """Context manager to skip signals for @instance (django model), @signals can be
    True to skip all signals or list of specified signals, like [post_delete, post_save] """
    try:
        yield setattr(instance, MUTE_SIGNALS_ATTR, signals)
    finally:
        setattr(instance, MUTE_SIGNALS_ATTR, False)

[signals.py]

@receiver(post_save, sender=Payment, dispatch_uid='post_payment_signal')
@mutable_signal_receiver
def handle_payment(sender, instance, created, **kwargs):
    """called after payment is registered in the system."""