Get last function's call arguments from traceback?

Question

Can I get the parameters of the last function called in traceback? How?

I want to make a catcher for standard errors to make readable code, yet provide detailed information to user.

In the following example I want GET_PARAMS to return me a tuple of parameters supplied to os.chown. Examining the inspect module advised by Alex Martelli, I couldn't find that.

def catch_errors(fn):
    def decorator(*args, **kwargs):
        try:
            return fn(*args, **kwargs)
        except (IOError, OSError):
            msg = sys.exc_info()[2].tb_frame.f_locals['error_message']
            quit(msg.format(SEQUENCE_OF_PARAMETERS_OF_THE_LAST_FUNCTION_CALLED)\
            + '\nError #{0[0]}: {0[1]}'.format(sys.exc_info()[1].args), 1)
    return decorator

@catch_errors
def do_your_job():
    error_message = 'Can\'t change folder ownership \'{0}\' (uid:{1}, gid:{2})'
    os.chown('/root', 1000, 1000) # note that params aren't named vars.

if __name == '__main__' and os.getenv('USERNAME') != 'root':
    do_your_job()

(Thanks to Jim Robert for the decorator)

Answer 1

The problem with using a decorator for what you're trying to achieve is that the frame the exception handler gets is do_your_job()s, not os.listdir()s, os.makedirs()s or os.chown()s. So the information you'll be printing out is the arguments to do_your_job(). In order to get the behavior I think you intend, you would have to decorate all the library functions you're calling.