How to prevent a block of code from being interrupted by KeyboardInterrupt in Python?

The following is a context manager that attaches a signal handler for SIGINT. If the context manager's signal handler is called, the signal is delayed by only passing the signal to the original handler when the context manager exits.

import signal
import logging

class DelayedKeyboardInterrupt(object):
    def __enter__(self):
        self.signal_received = False
        self.old_handler = signal.signal(signal.SIGINT, self.handler)

    def handler(self, sig, frame):
        self.signal_received = (sig, frame)
        logging.debug('SIGINT received. Delaying KeyboardInterrupt.')

    def __exit__(self, type, value, traceback):
        signal.signal(signal.SIGINT, self.old_handler)
        if self.signal_received:
            self.old_handler(*self.signal_received)

with DelayedKeyboardInterrupt():
    # stuff here will not be interrupted by SIGINT
    critical_code()

Put the function in a thread, and wait for the thread to finish.

Python threads cannot be interrupted except with a special C api.

import time
from threading import Thread

def noInterrupt():
    for i in xrange(4):
        print i
        time.sleep(1)

a = Thread(target=noInterrupt)
a.start()
a.join()
print "done"


0
1
2
3
Traceback (most recent call last):
  File "C:\Users\Admin\Desktop\test.py", line 11, in <module>
    a.join()
  File "C:\Python26\lib\threading.py", line 634, in join
    self.__block.wait()
  File "C:\Python26\lib\threading.py", line 237, in wait
    waiter.acquire()
KeyboardInterrupt

See how the interrupt was deferred until the thread finished?

Here it is adapted to your use:

import time
from threading import Thread

def noInterrupt(path, obj):
    try:
        file = open(path, 'w')
        dump(obj, file)
    finally:
        file.close()

a = Thread(target=noInterrupt, args=(path,obj))
a.start()
a.join()

Use the signal module to disable SIGINT for the duration of the process:

s = signal.signal(signal.SIGINT, signal.SIG_IGN)
do_important_stuff()
signal.signal(signal.SIGINT, s)