[Python-Dev] Fix import errors to have data

Brett C. bac at OCF.Berkeley.EDU
Wed Jul 28 01:58:02 CEST 2004

Neal Norwitz wrote:
> On Tue, Jul 27, 2004 at 12:39:22PM -0400, Jim Fulton wrote:
>>Tim Peters wrote:
>>>[Jim Fulton]
>>>>No, it won't.  For example, suppose foo imports B. B tries to import
>>>>C, but fails.  B is now broken, but it is still importable.  Actually,
>>>>both foo and B can be imported without errors, even though they are
>>>Then you're proposing a way for a highly knowledgable user to
>>>anticipate, and partially worm around,  that Python leaves behind
>>>insane module objects in sys.modules. 
>>No.  I'm proposing a way for a Python developer to detect the
>>presence or absence of a module.
>>Hm, perhaps it would be better to provide an API (if there isn't one
>>already) to test whether a module is present.
> Another possibility could be to add a ChainedImportError (or
> SubImportError?) which would derive from ImportError.  The module
> which imports a broken module would get the normal ImportError.  If
> the module doesn't catch the exception, it would get converted to this
> new type of ImportError.
> I don't know how easy this would be to implement, but I think it
> would solve Jim's problem and perhaps be easier to deal with?

Having exceptions keeping track of previous exceptions might also work. 
  I know that idea was brought up before last year (see 
for the historically accurate summary of the thread).  Idea died when no 
one could come up with a good way of storing previous exception info.


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