Hi Peter, You have identified the crux of the matter. Basically what happens is that the import apparently locks the interpreter so that the graphics thread does not get a chance to run (import is atomic?). So any call into the graphics library (like creating a GraphWin) deadlocks, since the call cannot return until the thread runs, and the thread won't run until the import is complete.
I could "fix" this by having my graphics package delay the thread launch until the first graphics call is made. But that means _every_ graphics operation will have to check to see if the thread has been launched yet. Even if that's not a big efficiency issue (I'm not sure), it feels too ad hoc to me, so I've resisted doing it. I may resort to that in the next release. By the way, I personally would pair the initGraphics() with a closeGraphics() operation that closes the window clean up at the end. --John On Monday 12 February 2007 10:59 am, Peter Drake wrote: > I tried just tacking all of my procedural wrappers on to the end of > your file so there would be no transitive import. Surprisingly, that > didn't work. The trick you mention below DOES work, and I'll use that > as a workaround. > > A clue, then: it's not the transitive importing that causes the > problem, it's the importing of a file that calls GraphWin(). > > Peter Drake > Assistant Professor of Computer Science > Lewis & Clark College > http://www.lclark.edu/~drake/ > > On Feb 9, 2007, at 1:09 PM, John Zelle wrote: > > Peter, > > > > I should have caught this when you posted your file. There is a > > bizarre import > > interaction that I am aware of, but can't say that I fully understand > > regarding my graphics library. It seems that Python imports are in > > some-way, > > somewhat atomic, and with the way my graphics library is set up > > this can > > produce this deadlock. I have a workaround for you. Move the > > graphics setup > > code in your module into a function: > > > > def initGraphics(): > > global root > > root = z.GraphWin() > > > > print "If you can't see the graphics window," > > print "it's probably at the upper left" > > print "of your screen, behind this one." > > > > Then call this function once at the start of your graphics > > programs. This is > > what will now pop up the window. So your "junk" program becomes: > > > > from graphics2 import * > > print "imported graphics2" > > initGraphics() > > background("red") > > > > If someone has a better understanding of Python module imports and > > why that > > causes a problem with my graphics package, I'd love to know how to > > fix this > > problem rather than working around it. > > > > --John > > > > On Friday 09 February 2007 1:36 pm, Peter Drake wrote: > >> The graphics2.py file I supplied earlier (http://www.lclark.edu/ > >> ~drake/courses/cs0/graphics2.py) is a procedural front-end for > >> Zelle's graphics.py. > >> > >> If I run the graphics2.py module, everything works fine, and I can > >> issue commands interactively. > >> > >> A problem happens if I write ANOTHER program, say junk.py: > >> > >> from graphics2 import * > >> print "imported graphics2" > >> background("red") > >> > >> When I run this (within IDLE), it hangs trying to import graphics2. > >> There is no error message or processor load, it just hangs. > >> > >> Can anyone explain (or reproduce) this behavior? > >> > >> Peter Drake > >> Assistant Professor of Computer Science > >> Lewis & Clark College > >> http://www.lclark.edu/~drake/ > >> > >> > >> > >> _______________________________________________ > >> Edu-sig mailing list > >> Edu-sig@python.org > >> http://mail.python.org/mailman/listinfo/edu-sig > > > > -- > > John M. Zelle, Ph.D. Wartburg College > > Professor of Computer Science Waverly, IA > > [EMAIL PROTECTED] (319) 352-8360 > > _______________________________________________ > > Edu-sig mailing list > > Edu-sig@python.org > > http://mail.python.org/mailman/listinfo/edu-sig > > _______________________________________________ > Edu-sig mailing list > Edu-sig@python.org > http://mail.python.org/mailman/listinfo/edu-sig -- John M. Zelle, Ph.D. Wartburg College Professor of Computer Science Waverly, IA [EMAIL PROTECTED] (319) 352-8360 _______________________________________________ Edu-sig mailing list Edu-sig@python.org http://mail.python.org/mailman/listinfo/edu-sig
