CODEWITHSUNDEEP
python
I_Literally_Cannot
I_Literally_Cannot

Reputation: 170

How to continuously run a python script until an output is printed?

I am trying to get a python program to continuously run until a certain aws log is registered and printed. It is supposed to:

  1. Run indefinitely even if no events happen
  2. List whatever events occurs (in my case a log stating that the task is finished)
  3. Stop running

the python command looks like this: python3 watch_logs.py <log-source> --start=15:00:00

The logs are working fine, and the python script can print them out between certain time frames as long as they already exist. The program works by taking a continuously running task which prints events to the log file, and the python script should filter out events I am looking for and print them.

But, when I run the script, it wont print the event even if I can see the log entry appear in the file. If i kill the process and run it again using the same timestamp, it will find the log entry and end the script like it should.

the code is fairly short: 

logs = get_log_events(
                log_group=log_group,
                start_time=start_time,
                end_time=end_time
            )
while True:
    for event in logs:
        print(event['message'].rstrip())
        sys.exit("Task complete")

Any insight why this is happening would help a lot. I am fairly new to python

Upvotes: 0

Views: 1605

Answers (4)

I_Literally_Cannot
I_Literally_Cannot

Reputation: 170

I was overthinking the problem. I put the log variable inside the loop so it was being defined at each cycle


while True:
    logs = get_log_events(
        log_group=log_group,
        start_time=start_time,
        end_time=end_time
        )
        for event in logs:
            print(event['message'].rstrip())
            sys.exit("Task complete")

Upvotes: 0

Hans-Martin Mosner
Hans-Martin Mosner

Reputation: 856

If you don't want to read the file each time through the loop, you should have a look at pygtail (https://pypi.org/project/pygtail/).

Upvotes: 0

Orion
Orion

Reputation: 496

The value in the variable logs is old when the file is updated. You need to update this variable. For example if you were to use logs = myfile.read() at start of your script, the value in the logs variable would be a snapshot of that file at that time.

Upvotes: 1

PMM
PMM

Reputation: 376

Try storing event['message'].rstrip() in a variable and checking with an if statement if it corresponds to the log you want to find

Upvotes: 0

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