How to “stop” and “resume” long time running Python script?

Question

I wrote Python script that processes big number of large text files and may run a lot of time. Sometimes, there is a need to stop the running script and to

Answer 1

The execution could sleep it's life away, or (aside from the exceptions of security), the state of the script can be pickled, zipped, and stored.

http://docs.python.org/library/pickle.html

http://docs.python.org/library/marshal.html

http://docs.python.org/library/stdtypes.html (5.9)

http://docs.python.org/library/archiving.html

http://www.henrysmac.org/?p=531

Answer 2

Here is something simple that hopefully can help you:

import time
import pickle


REGISTRY = None


def main(start=0):
    """Do some heavy work ..."""

    global REGISTRY

    a = start
    while 1:
        time.sleep(1)
        a += 1
        print a
        REGISTRY = pickle.dumps(a)


if __name__ == '__main__':
    print "To stop the script execution type CTRL-C"
    while 1:
       start = pickle.loads(REGISTRY) if REGISTRY else 0
        try:
            main(start=start)
        except KeyboardInterrupt:
            resume = raw_input('If you want to continue type the letter c:')
            if resume != 'c':
                break

Example of running:

$ python test.py
To stop the script execution type CTRL-C
1
2
3
^CIf you want to continue type the letter c:c
4
5
6
7
8
9
^CIf you want to continue type the letter c:
$ python test.py

Answer 3

If you are looking to read big files, just use a file handle, and read the lines one at a time, processing each line as you need to. If you'd like to save the python session, then just use dill.dump_session -- and it will save all existing objects. Other answers will fail as pickle cannot pickle a file handle. dill, however, can serialize almost every python object -- including a file handle.

Python 2.7.9 (default, Dec 11 2014, 01:21:43) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> f = open('bigfile1.dat', 'r')
>>> data = f.readline()  
>>> 
>>> dill.dump_session('session.pkl')
>>> 

Then quit the python session, and restart. When you load_session, you load all the objects that existed at the time of the dump_session call.

dude@hilbert>$ python
Python 2.7.9 (default, Dec 11 2014, 01:21:43) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> dill.load_session('session.pkl')
>>> len(data)
9
>>> data += f.readline()
>>> f.close()
>>> 

Simple as that.

Get dill here: https://github.com/uqfoundation