Bill Burns wrote: > I've got a few questions regarding Threading. I've never used threads > before and I want to make sure I'm doing it correctly ;-) > > I have a GUI app and it processes Tiff files to PDF (or PostScript). The > GUI has a ListBox which the user populates with files to convert. You > click on a Button and the file conversion starts. When all the files > have been converted, the ListBox items (the files) are cleared. > > Initially, you had no way of knowing what was going on until all the > files where cleared from the ListBox. > > So I thought of creating threads in the 'for loop' and displaying the > name of each file in the statusBar of the GUI (as they are being > processed).
You don't necessarily need threads for this. If you just want to provide feedback and don't care about the GUI being responsive, just do the processing in a loop, update the status bar and call root.update_idletasks() to allow the GUI to redraw. (Assuming you are using Tkinter.) If you want the GUI to remain responsive so for example you can have a Cancel button, then I would make a single thread and process all the files in that thread. Don't sleep in the thread; call root.update() to give some time to event handling. Somehow you will have to notify the main thread that the worker thread is done. The only reason I can think of to make a separate thread for each image is if the process is significantly I/O bound. My guess is that Tiff to PDF conversion is CPU-intensive and a single worker thread will be plenty. More notes below... > Here's my method which takes the files in the ListBox and sends them off > to my Convert() class (self.convert = Convert()). > <code> > def convertTiff2PDF(self): > from time import time > #Let's see how long this takes... I saw Kent do this on the > #Python Tutor list before :-) > start = time() > #Grab a tuple which contains width & length > sizes = self.getPaperSize() > width = sizes[0] > length = sizes[1] > #Count the number of files in the ListBox > fileCount = self.fileListBox.count() > for index in range(fileCount): > #Get each filename > filenames = str(self.fileListBox.text(index)) > #Setup the worker thread and send the filenames in > worker = WorkerThread(self, filenames) > #Start threading > worker.start() > #Send each file to be converted > self.convert.tiff2pdf(width, length, filenames) The above line should be in the thread, not in the main loop - you are spawning threads that do nothing but update the status display - and they will compete for that. > #We're done, so clear the ListBox > self.fileListBox.clear() > #Check the time again > end = time() > msg = '%s Files Processed in %0.3f Seconds.' % (fileCount, > (end-start)) > #Grab the statusBar and insert the message > statusBar = self.statusBar() > statusBar.message(msg, 0) > </code> > > And here's what I'm doing in my Thread class: > <code> > class WorkerThread(Thread): > """Thread class.""" > def __init__(self, parent, files): > Thread.__init__(self) > self.parent = parent > self.files = files > > def run(self): > statusBar = self.parent.statusBar() > msg = 'Processing: %s, please wait.' % (self.files) > statusBar.message(msg, 100) > time.sleep(1) > </code> > > Am I doing this threading properly? Is it 'OK' to start multiple threads > like this (in the for loop)? It's possible that a user could put 'many' > files into the ListBox, by 'many' I mean 100-200 files. It's OK to have multiple threads but yours aren't doing any useful work. I hope this helps get you on track, it's a bit brief. Kent > > Thanks for your help. > > Bill > > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
