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Sun Jul 30 23:34:30 CEST 2006 · https://mail.python.org/pipermail/python-dev/2006-July/067847.html

Fred L. Drake, Jr. schrieb:
> On Sunday 30 July 2006 15:44, Barry Warsaw wrote:
>  > if isinstance(obj, ClassType) or isinstance(obj, type(type))
> 
> Looks like you've got a possible name clash in the second isinstance.  ;-)

Nah, that's rather an entry to the obfuscated Python contest.
The two occurrences of type really mean to refer to the same
thing; this is the test whether obj _is a_ new-style class.

Normally, you would write isinstance(obj, type), but that gives
a TypeError in 2.1 (isinstance() arg 2 must be a class or type).
In 2.1, type(type) is FunctionType, so the test should
fail (in the context, as obj ought to be a string, an exception
object, or an exception type). In 2.2 and later, we have

>>> type(type) is type
1 # sometimes True instead

I think I would have rewritten as

try:
  # Instantiate it if possible and necessary
  exc = exc()
except AttributeError: # no __call__; it's already an object
  pass

(assuming that the mailman exceptions don't have __call__) or as

if not isinstance(exc, Exception):
   exc = exc()

(assuming that string exceptions are gone, but the code below
 already assumes that exc should be an object that supports
 exc.reason_notice())

Regards,
Martin

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