How to Get a Stack Trace of a Running Python Application?

Inspecting Stack Trace of a Running Python Application

When a Python application unexpectedly hangs, it can be challenging to determine the source of the issue. Fortunately, there are techniques to obtain a stack trace of the running application, allowing you to pinpoint the specific code being executed when the application halts.

Using a Custom Signal Handler

One method to show a stack trace is to use a custom signal handler. This technique involves sending a signal to the running application, triggering the handler to capture the stack trace and display it interactively. Below is an example using the debug function:

<code class="python">import code, traceback, signal

def debug(sig, frame):
    d={'_frame':frame}         
    d.update(frame.f_globals)  
    d.update(frame.f_locals)

    i = code.InteractiveConsole(d)
    message  = "Signal received : entering python shell.\nTraceback:\n"
    message += ''.join(traceback.format_stack(frame))
    i.interact(message)

def listen():
    signal.signal(signal.SIGUSR1, debug)  </code>

Once the listen() function is invoked, sending a SIGUSR1 signal to the process using os.kill or kill will interrupt the running application, providing a Python console with the stack trace.

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