Get exception description and stack trace which caused an exception, all as a string

Question

I've seen a lot of posts about stack trace and exceptions in Python. But haven't found what I need.

I have a chunk of Python 2.7 code that may raise an exception. I would like to catch it and assign to a string its full description and the stack trace that caused the error (simply all we use to see on the console). I need this string to print it to a text box in the GUI.

Something like this:

try:     method_that_can_raise_an_exception(params) except Exception as e:     print_to_textbox(complete_exception_description(e)) 

The problem is: what is the function complete_exception_description?

Answer 1

See the traceback module, specifically the format_exc() function. Here.

import traceback  try:     raise ValueError except ValueError:     tb = traceback.format_exc() else:     tb = "No error" finally:     print tb 

Answer 2

Let's create a decently complicated stacktrace, in order to demonstrate that we get the full stacktrace:

def raise_error():     raise RuntimeError('something bad happened!')  def do_something_that_might_error():     raise_error() 

Logging the full stacktrace

A best practice is to have a logger set up for your module. It will know the name of the module and be able to change levels (among other attributes, such as handlers)

import logging logging.basicConfig(level=logging.DEBUG) logger = logging.getLogger(__name__) 

And we can use this logger to get the error:

try:     do_something_that_might_error() except Exception as error:     logger.exception(error) 

Which logs:

ERROR:__main__:something bad happened! Traceback (most recent call last):   File "<stdin>", line 2, in <module>   File "<stdin>", line 2, in do_something_that_might_error   File "<stdin>", line 2, in raise_error RuntimeError: something bad happened! 

And so we get the same output as when we have an error:

>>> do_something_that_might_error() Traceback (most recent call last):   File "<stdin>", line 1, in <module>   File "<stdin>", line 2, in do_something_that_might_error   File "<stdin>", line 2, in raise_error RuntimeError: something bad happened! 

Getting just the string

If you really just want the string, use the traceback.format_exc function instead, demonstrating logging the string here:

import traceback try:     do_something_that_might_error() except Exception as error:     just_the_string = traceback.format_exc()     logger.debug(just_the_string) 

Which logs:

DEBUG:__main__:Traceback (most recent call last):   File "<stdin>", line 2, in <module>   File "<stdin>", line 2, in do_something_that_might_error   File "<stdin>", line 2, in raise_error RuntimeError: something bad happened!