What is Python replacement for PHP's error_get_last() function?

Question

I need to implement an atexit Python function that would get the last error object and check for it's type. If the type of python error corresponds to PHP's E_ERROR I should save the error's output to a file.

The PHP code I'm porting looks like so:

register_shutdown_function( "fatal_handler" );
function fatal_handler() {
  $error = error_get_last();
    if ($error != null && $error['type'] === E_ERROR)
        echo  "recordFatalError: {$error['message']}\n";
}

My code snap are as follows:

def fatal_handler():
   # How to get last error object?

atexit.register(fatal_handler)

I would be glad if somebody explained me how can I get the necessary functionality with python.

Answer 1

I would use sys.last_value for this:

import atexit
import sys

def fatal_handler():
    try:
        e = sys.last_value
    except AttributeError: # no exception prior to execution of fatal_handler
        return

atexit.register(fatal_handler)

You may choose to use getattr(sys, 'last_value', None) in place of the EAFP approach above. It returns None if sys.last_value isn't available.

Alternatively, if there's just one function you want to run only when the interpreter shutdown is caused by an exception, you could use sys.excepthook:

import sys

def fatal_handler(type, value, traceback):
   e = value

sys.excepthook = fatal_handler

Answer 2

When an exception is raised and uncaught, the interpreter calls sys.excepthook with info about the exception. The default function prints out a given traceback and exception to sys.stderr. You can replace this function with a function which save this data. Later you can use this data in your atexit handler:

import atexit
import sys

class LastException:
    value     = None
    type      = None
    trackback = None

    @staticmethod
    def excepthook(type,value,trackback):
        LastException.type      = type
        LastException.value     = value
        LastException.trackback = trackback

    @staticmethod
    def register():
        sys.excepthook = LastException.excepthook

def fatal_handler():
   print('{0} {1}'.format( LastException.type, LastException.value))

LastException.register()
atexit.register(fatal_handler)

raise BaseException("I am an error") 
# should print: <class 'BaseException'> I am an error