This has gotten more and more bizarre.
I can get the images to appear while running under the debugger (Wing) *if*
I set a breakpoint almost anywhere within either:
(1) the method that inserts the item into the list, or
(2) within the __init__ method of the class containing that insertion
method.
Once the breakpoint is hit and I continue, then the images appear in the
result display of the list. And when I add other things to the list the
images appear as well. If I run outside the debugger, the images do not
appear.
However ... If I instead set the breakpoint *before* instantiating that
class or *after* instantiation, the images do not appear.
Further ... If in addition to the original breakpoint (which by itself
results in the images being displayed) I set an *additional* one after the
class has been instantiated, the images do *not* appear -- like whatever
happens with the first breakpoint is cancelled when the second is also
present.
In my experience, this kind of behavior under a debugger is almost always a
symptom of a pointer being wrong somewhere, of data structures overlapping
in memory, etc. Though in an event-driven context it could also have
something to do with the interaction of various events. I can't see
anything obviously wrong with my code.
I'm willing to spend some more time chasing this (using print statements
since using the debugger is giving me some Heisenberg-like uncertainty
effects 
). But I'd appreciate any other thoughts or speculations at
this point.
···
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Gary H. Merrill
Director and Principal Scientist, New Applications
Data Exploration Sciences
GlaxoSmithKline Inc.
(919) 483-8456