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.

lvc · Accepted Answer · 2012-04-20 14:52:13Z

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, 2012 at 14:52

lvc

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2 Comments

ch3ka Over a year ago

nice, but py3 only. anyways: +1.

Claudiu Over a year ago

ah, nice. so according to that PEP, the answer is, "you can't, in Py2, but you can in Py3". thanks!

ThiefMaster · Accepted Answer · 2012-04-20 14:45:46Z

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, 2012 at 14:45

ThiefMaster

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1 Comment

Mechanical snail Over a year ago

That just swallows the "in the try" exception before it gets to the finally block.

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