[Delaney, Timothy C (Timothy)]
OK - the problem as I see it is that a given module that exists, but raises ImportError, only raises ImportError *once*, whereas it really should raise ImportError every time
Jim's after something different, while the problem you're thinking about is more general than just ImportError. When an import of an existing module fails for *any* reason, subsequent attempts to import the same module succeed. For example,
C:\Code>type a.py 1/0
C:\Code>\python23\python.exe Python 2.3.4 (#53, May 25 2004, 21:17:02) [MSC v.1200 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information.
import a
Traceback (most recent call last): File "<stdin>", line 1, in ? File "a.py", line 1, in ? 1/0 ZeroDivisionError: integer division or modulo by zero
import a
This is Bad, because an uncaught exception in module initialization means the module probably can't fulfill its contract, yet subsequent importers get no clue that the module is in a damaged state (until the module fails to do its job, which may or may not be obvious when it occurs). A module failing to import because it suffers an ImportError itself is once instance of this, but the same applies to a module failing to import for any other reason: in all these cases, subsequent imports don't get the exception the initial importer saw, they get a module object in an arbitrarily screwed-up state.