Can I get the exception from the finally block in python?

Question

I have a try/finally clause in my script. Is it possible to get the exact error message from within the finally clause?

Answer 1

Actually, other answers are bit vague. So, let me clarify it. You can always invoke sys.exc_info() from finally block. However, its output will vary depending whether exception has been actually raised.

import sys

def f(i):

    try:
        if i == 1:
            raise Exception
    except Exception as e:
        print "except -> " + str(sys.exc_info())
    finally:
        print "finally -> " + str(sys.exc_info())

f(0)
f(1)

>>> 
finally -> (None, None, None)
except -> (, Exception(), )
finally -> (, Exception(), )

Thus, you can always know in finally block, whether exception was raised, if it's first level function. But sys.exc_info() will behave differently when length of call stack exceeds 1, as shown in below example. For more information, refer to How sys.exc_info() works?

import sys

def f(i):

    try:
        if i == 1:
            raise Exception
    except Exception as e:
        print "except -> " + str(sys.exc_info())
    finally:
        print "finally -> " + str(sys.exc_info())

def f1(i):
    if i == 0:
        try:
            raise Exception('abc')
        except Exception as e:
            pass

    f(i)

f1(0)
f1(1)

>>> 
finally -> (, Exception('abc',), )
except -> (, Exception(), )
finally -> (, Exception(), )

I hope, it makes things bit clearer.