Can't catch SystemExit exception Python

Question

I am trying to catch a SystemExit exception in the following fashion:

try:
    raise SystemExit
except Exception as exception:
    print "success"

But, it doesn't work.

It does work however when I change my code like that:

try:
    raise SystemExit
except:
    print "success"

As far as I am aware, except Exception as exception should catch any exception. This is how it is described here as well. Why isn't that working for me here?

Adam Nelson · Accepted Answer · 2016-06-14 20:50:41Z

53

As documented, SystemExit does not inherit from Exception. You would have to use except BaseException.

However, this is for a reason:

The exception inherits from BaseException instead of StandardError or Exception so that it is not accidentally caught by code that catches Exception.

It is unusual to want to handle "real" exceptions in the same way you want to handle SystemExit. You might be better off catching SystemExit explicitly with except SystemExit.

edited Jun 14, 2016 at 20:50

Adam Nelson

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answered Oct 29, 2014 at 4:57

BrenBarn

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1 Comment

Eugene S Over a year ago

Perfect. Thanks! It is very well illustrated in the documentation Exception hierarchy: docs.python.org/2/library/exceptions.html#exception-hierarchy

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