Python installs its own SIGINT handler in order to raise KeyboardInterrupt exceptions. Setting the signal to SIG_DFL will not restore that handler, but the "standard" handler of the system itself (which terminates the interpreter).

You have to store the original handler and restore that handler when you're done:

original_sigint_handler = signal.getsignal(signal.SIGINT)

# Then, later...
signal.signal(signal.SIGINT, original_sigint_handler)

As kindall rightfully says in comments, you can express this as a context manager:

from contextlib import contextmanager

@contextmanager
def sigint_ignored():
    original_sigint_handler = signal.getsignal(signal.SIGINT)
    signal.signal(signal.SIGINT, signal.SIG_IGN)
    try:
        print('Now ignoring CTRL-C')
        yield
    except:
        raise  # Exception is dropped if we don't reraise it.
    finally:
        print('Returning control to default signal handler')
        signal.signal(signal.SIGINT, original_sigint_handler)

You can use it like this:

# marker 1
print('No signal handler modifications yet')
print('Sleeping...')
time.sleep(10)

# marker 2
with sigint_ignored():
    print('Sleeping...')
    time.sleep(10)

# marker 3
print('Sleeping...')
time.sleep(10)

What about implementing your signal handling code inside a class? This could look something like the following:

class GracefulExit:
    def __enter__(self):
        # set up signals here
        # store old signal handlers as instance variables

    def __exit__(self, type, value, traceback):
        # restore old signal handlers

You can then use this in your code as follows:

with GracefulExit():
    # Signals will be caught inside this block.

# Signals will no more be caught here.

You'll find more examples of how to use the with-statement on the web.

The line you commented out (self.signalReceiver.remove()) works.

add_signal_receiver() returns a SignalMatch instance on which you can call remove() method to unregister your callback.

The problem in your code snippet is that dbusA.run() is a blocking call because it calls self.mainloop.run() which itself is a blocking call.

This said, program execution will never reach dbusA.end(), thus signal unregistering and quitting the run loop will not happen. You can however call this method from a different thread, or from any event handler of your dbus connection.