python try except 0

Question

I am reading some python code written a while ago, and found this:

try:
    # do some stuff
except 0:
    # exception handling stuff

And I'm just not sure what except 0 means? I do have my guesses: Supposed to catch nothing i.e. let the exception propagate or it could be some sort of switch to turn debugging mode on and off by removing the 0 which will then catch everything.

Can anyone lend some insight? a google search yielded nothing...

Thanks!

Some sample code (by request):

            try:
                if logErrors:
                    dbStuffer.setStatusToError(prop_id, obj)
                    db.commit()
            except 0:
                traceback.print_exc()

Answer 1

From the Python docs:

"[...] the [except] clause matches the exception if the resulting object is “compatible” with the exception. An object is compatible with an exception if it is the class or a base class of the exception object, or a tuple containing an item compatible with the exception."

In effect the type of the expression is used to determine whether the except clauses matches the exception. As 0 is of an integer type, and exception of that type would match.

Since integers cannot be raised as exception, this is a disabled exceptclass that will not catch anything.

Answer 2

From what I understand, This is very useful for debugging purposes (Catching the type of exception)

In your example 0 acts as a placeholder to determine the type of exception.

>>> try:
...   x = 5/1 + 4*a/3
... except 0:
...   print 'error'
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
NameError: name 'a' is not defined
>>> try:
...   x = 5/0 + 4*a/3
... except 0:
...   print 'error'
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ZeroDivisionError: integer division or modulo by zero

In the first case, the exception is NameError and ZeroDivisionError in the second. the 0 acts as a placeholder for any type of exception being caught.

>>> try:
...   print 'error'
... except:
... 
KeyboardInterrupt
>>> try:
...   x = 5/0 + 4*a/3
... except:
...   print 'error'
... 
error