Delay the keyboard interrupt in Python for an important part of the program

Question

What is the method to delay the keyboard interrupt for an important part of the program (in my example in a cycle).

I want to download (or save) many files, and if it takes too long, I want to finish the program, when the recent file have been downloaded.

Need I to use the signal module as in the answer for Capture keyboardinterrupt in Python without try-except? Can I set a global variable to True with the signal handler and break the cycle if it is True?

The original cycle is:

for file_ in files_to_download:
    urllib.urlretrieve("".join(baseurl, file_), os.path.join(".", file_))

Andrew Clark · Accepted Answer · 2012-11-02 16:45:10Z

5

Something like the following may work:

# at module level (not inside class or function)
finish = False
def signal_handler(signal, frame):
    global finish
    finish = True

signal.signal(signal.SIGINT, signal_handler)

# wherever you have your file downloading code (same module)
for file_ in files_to_download:
    if finish:
        break
    urllib.urlretrieve("".join(baseurl, file_), os.path.join(".", file_))

answered Nov 2, 2012 at 16:45

Andrew Clark

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4 Comments

Arpad Horvath -- Слава Україні Over a year ago

It is easy. I should try it instead of ask.

Eryk Sun Over a year ago

@ArpadHorvath: If you have multiple modules in a package, you could bundle your signal handlers in a class. Make each handler a classmethod so it can easily set class attributes such as cls.finish. Then, for example, check SignalState.finish in your loop if the class is named SignalState.

Arpad Horvath -- Слава Україні Over a year ago

I can set the original state for the interrupt with the signal.signal(signal.SIGINT, signal.default_int_handler). I should set my handler before the important part, and set the default handler after that. Am I right?

Arpad Horvath -- Слава Україні Over a year ago

I made a module based upon the answer of F.J and eryksun: gist.github.com/4006374 The SafeInterruptHandler class has an off and on classmethod to swich off and on the special behaviour, and a decorator method to create safe functions. Thanks.

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