Is there a way to access variables after an error when running Python

Question

I am using Pycharm Community 4.5.4. I am running a program that takes a very long time to complete.

Unfortunately, I have a print statement that comes before the line that saves the data accumulated which has an error. I ran the print line by itself and confirmed that the line will fail.

It is possible that I made the change after I ran the program and so it won't fail but I can't be sure. The portion of code takes about 90 hours to complete and I have about 30 left if the execution time stays around the average.

So, if it fails, is there any way to recover the data?

Just to be clear, I am running and not debugging. Also, I am line profiling to see how each 2.5 hour iteration's time is spent.

if you have run this in a console, you can use pdb.pm() to break into the failing context (don't forget import pdb first - always annoying when I forget, and now the last error is that it didn't know what pdb was :) and look at things, save, etc. Or (I don't know pycharm) you may be able to put a breakpoint there. If you ran it standalone though, there's no way. — Corley Brigman
– Corley Brigman, Commented Sep 8, 2015 at 15:13
You can use stackoverflow.com/questions/242485/… in your main process. And use jetbrains.com/pycharm/help/attaching-to-process.html to attach to the main process. — Ali SAID OMAR
– Ali SAID OMAR, Commented Sep 8, 2015 at 15:27
@AliSAIDOMAR I was able to use the 'Attach to process...' and then use the 'Evaluate Code Fragment' (Alt+F8) to import additional modules (Pickle) and dump the value of a variable at a breakpoint that I set. Will you submit your comment as an answer so I can give you the credit? Thanks soooo much. — Chris
– Chris, Commented Sep 8, 2015 at 15:44

Community · Accepted Answer · 2017-05-23 10:32:32Z

2

So I told, you shoud update your main module to exit on the breakpoint

import pdb
import random
import time
import os
import traceback
import sys


def main(*args, **kw):
    for i in range(10):
        print("OK I'm in %d" % os.getpid())
        time.sleep(4)
        if i == 9:
            raise Exception

if __name__ == '__main__':
    try:
        main()
    except:
        type, value, tb = sys.exc_info()
        traceback.print_exc()
        pdb.post_mortem(tb)

Starting python debugger automatically on error Credit.

And use Pycharm attach to process. if an error is raised so you will be able to debug with pycharm.

edited May 23, 2017 at 10:32

CommunityBot

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answered Sep 8, 2015 at 16:11

Ali SAID OMAR

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1 Comment

Chris Over a year ago

I should add that in the OP the program in question is actually still running. This situation is rare, but the program will run for ~90 hours. This means that I would need to break into a currently running program and be able to access the data. Using the information you left in the comment above, I was able to do this. Your answer works great if I could start over but the whole point was to avoid starting over and losing the data. It is possible, like I said in the comment above, to attach to a currently running process and use Run | Evaluate Expression... to import, save, or whatever.

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