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.

Answer 1

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 "", line 2, in 
  File "", line 2, in do_something_that_might_error
  File "", 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 "", line 1, in 
  File "", line 2, in do_something_that_might_error
  File "", 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 "", line 2, in 
  File "", line 2, in do_something_that_might_error
  File "", line 2, in raise_error
RuntimeError: something bad happened!