python：如果finally块引发异常，则从try块恢复异常

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.

Answer 1

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.

Answer 2

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.