This seems to be a very weird behavior. After modifying a file, all instantiated instances V of classes C in the file are no longer correct (i.e. instance(V,C) returns false).
Here's a simple example illustrating the problem I have a file called t1.py contains the following class Test(object): def __init__(self): pass Now open sage, at the prompt do $ sage ---------------------------------------------------------------------- | Sage Version 4.8, Release Date: 2012-01-20 | | Type notebook() for the GUI, and license() for information. | ---------------------------------------------------------------------- sage: attach t1.py sage: t = Test() sage: isinstance(t,Test) True #### here it's correct Now go back to the file t1.py, make any modification , e.g. enter a space and delete it ... save the file sage: isinstance(t,Test) False #### here it's no longer correct -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org