[Bug 43095] Re: Mayavi does not start (dependency problem ?)

[Jérémie Corbier]

Does Mayavi use the Patented code? It was removed from Debian vtk about 4 years ago. I don't think the bug is Patented related.

In fact when a module is not found the exception is handled by __helper.refine_import_err(mod_name, exc). In that function there is "del sys.modules['vtk.%s'%mod_name]" which is supposed to remove the module name from the already imported modules list. I think it was a workaround for a bug fixed in Python a while ago. Here is a quote from /usr/share/doc/python2.4/NEWS.gz

"When importing a module M raises an exception, Python no longer leaves M
  in sys.modules.  Before 2.4a2 it did, and a subsequent import of M would
  succeed, picking up a module object from sys.modules reflecting as much
  of the initialization of M as completed before the exception was raised.
  Subsequent imports got no indication that M was in a partially-
  initialized state, and the importers could get into arbitrarily bad
  trouble as a result (the M they got was in an unintended state,
  arbitrarily far removed from M's author's intent).  Now subsequent
  imports of M will continue raising exceptions."

A fix for this bug would be to remove the del sys.modules["..."] part.

-- 
Mayavi does not start (dependency problem ?)
https://launchpad.net/bugs/43095