python: recover exception from try block if finally block raises exception

Question

Say I have some code like this:

try:
    try:
        raise Exception("in the try")
    finally:
        raise Exception("in the finally")
except Exception, e:
    print "try block failed: %s" % (e,)

The output is:

try block failed: in the finally

From the point of that print statement, is there any way to access the exception raised in the try, or has it disappeared forever?

NOTE: I don't have a use case in mind; this is just curiosity.

score 14 · Accepted Answer · answered Apr 20 '12 at 14:52

14

I can't find any information about whether this has been backported and don't have a Py2 installation handy, but in Python 3, e has an attribute called e.__context__, so that:

try:
    try:
        raise Exception("in the try")
    finally:
        raise Exception("in the finally")
except Exception as e:
    print(repr(e.__context__))

gives:

Exception('in the try',)

According to PEP 3314, before __context__ was added, information about the original exception was unavailable.

answered Apr 20 '12 at 14:52

lvc

34,233
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nice, but py3 only. anyways: +1. – ch3ka Apr 20 '12 at 14:57
1

ah, nice. so according to that PEP, the answer is, "you can't, in Py2, but you can in Py3". thanks! – Claudiu Apr 20 '12 at 15:26

score 0 · Answer 2 · answered Apr 20 '12 at 14:45

0

try:
    try:
        raise Exception("in the try")
    except Exception, e:
        print "try block failed"
    finally:
        raise Exception("in the finally")
except Exception, e:
    print "finally block failed: %s" % (e,)

However, It would be a good idea to avoid having code that is likely to throw an exception in the finally block - usually you just use it to do cleanup etc. anyway.

answered Apr 20 '12 at 14:45

ThiefMaster

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2

That just swallows the `"in the try"` exception before it gets to the finally block. – Mechanical snail Aug 22 '13 at 07:45

python: recover exception from try block if finally block raises exception

2 Answers2