On 2006-11-25, Gabriel Genellina <[EMAIL PROTECTED]> wrote: >>I'm just getting started on threading and was wondering why the >>following code does not work (i know globals is bad style - I'll >>eliminate them eventually). All I get is a blank cursor flashing. > > You've got your example already working. Globals are bad > style, but worse, threads and globals don't mix very well: you > need some sort of syncronization for accessing globals > (specially for writing them).
That depends on the type of the global and how they're used. Re-binding a name is always an atomic operation. Modifying many mutable objects is atomic. >>class ImapThread(threading.Thread): >> def run(self): >> global g_currenttick >> if time.time() > (g_datum + (g_secondspertick * >>g_currenttick)): >> print "Ticked %s" % g_currenttick >> g_currenttick=g_currenttick+1 >> print g_currenttick > > Having more than one thread, g_currenttick could have been modified > *after* you read its value and *before* you write it back, so you > lose the count. Right. Reading an integer object in one statement and writing it in a subsequent statement is not an atomic opteration unless protected by some synchronization mechanism. -- Grant Edwards [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
