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Use threads or Tkinter event loop?

P: n/a
I'm trying to decide whether I need threads in my Tkinter application or
not. My app is a front end to a command-line tool; it feeds commands to
the command-line program, then reads its output and displays it in a
Tkinter text widget. Some of the commands are long-running and/or return
thousands of lines of output.

I initially thought I needed to use threading, because the GUI would
block when reading the output, even when I configured the blocking to be
non-blocking. I got threading to work, but it seemed a bit complicated.
So, I decided to try something simpler, by using the Tkinter event loop
to force the output to update/display.

it seems to work well enough. Here is my threaded code:

non-threaded:

def insertDump(self):
self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
for line in self.finkinstalled:
self.t.insert(END, line)
self.update()
self.t.see(END)

And here is my non-threaded code (needs two functions to work)

def insertDump(self):
try:
data = self.dataQueue.get(block=False)
for line in data:
self.t.insert(END, line)
self.t.see(END)
self.update()
except:
print "error"
raise

def getDump(self):

self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
self.dataQueue.put(self.file)

This brings me to a design, as opposed to coding, question. The
non-threaded version seems to work just as well as the threaded one, in
terms of speed. Moreover, it is simpler to code and debug, because I
don't have to check to make sure the thread queue has data (I sometimes
get an 'Empty' error message when I first start the thread). Simply
using the Tk event loop (self.update) is also how I would have coded
this in Tcl.

So my question is this: under what circumstances in Python are threads
considered "best practice"? Am I wrong to use the Tk event loop instead
of threads?

--
Kevin Walzer
Code by Kevin
http://www.codebykevin.com
Mar 27 '07 #1
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2 Replies


P: n/a
Kevin Walzer wrote:
I'm trying to decide whether I need threads in my Tkinter application or
not. My app is a front end to a command-line tool; it feeds commands to
the command-line program, then reads its output and displays it in a
Tkinter text widget. Some of the commands are long-running and/or return
thousands of lines of output.

I initially thought I needed to use threading, because the GUI would
block when reading the output, even when I configured the blocking to be
non-blocking. I got threading to work, but it seemed a bit complicated.
So, I decided to try something simpler, by using the Tkinter event loop
to force the output to update/display.

it seems to work well enough. Here is my threaded code:

non-threaded:

def insertDump(self):
self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
for line in self.finkinstalled:
self.t.insert(END, line)
self.update()
self.t.see(END)

And here is my non-threaded code (needs two functions to work)

def insertDump(self):
try:
data = self.dataQueue.get(block=False)
for line in data:
self.t.insert(END, line)
self.t.see(END)
self.update()
except:
print "error"
raise

def getDump(self):

self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
self.dataQueue.put(self.file)

This brings me to a design, as opposed to coding, question. The
non-threaded version seems to work just as well as the threaded one, in
terms of speed. Moreover, it is simpler to code and debug, because I
don't have to check to make sure the thread queue has data (I sometimes
get an 'Empty' error message when I first start the thread). Simply
using the Tk event loop (self.update) is also how I would have coded
this in Tcl.

So my question is this: under what circumstances in Python are threads
considered "best practice"? Am I wrong to use the Tk event loop instead
of threads?
D'oh, I got the code snippets mixed up:

non-threaded:

def insertDump(self):
self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
for line in self.finkinstalled:
self.t.insert(END, line)
self.update()
self.t.see(END)

threaded:

def insertDump(self):
try:
data = self.dataQueue.get(block=False)
for line in data:
self.t.insert(END, line)
self.t.see(END)
self.update()
except:
print "error"
raise

def getDump(self):

self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
self.dataQueue.put(self.file)

Sorry!
--
Kevin Walzer
Code by Kevin
http://www.codebykevin.com
Mar 27 '07 #2

P: n/a
On Mar 27, 9:07 am, Kevin Walzer <k...@codebykevin.comwrote:
Kevin Walzer wrote:
I'm trying to decide whether I need threads in my Tkinter application or
not. My app is a front end to a command-line tool; it feeds commands to
the command-line program, then reads its output and displays it in a
Tkinter text widget. Some of the commands are long-running and/or return
thousands of lines of output.
I initially thought I needed to use threading, because the GUI would
block when reading the output, even when I configured the blocking to be
non-blocking. I got threading to work, but it seemed a bit complicated.
So, I decided to try something simpler, by using the Tkinter event loop
to force the output to update/display.
it seems to work well enough. Here is my threaded code:
non-threaded:
def insertDump(self):
self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
for line in self.finkinstalled:
self.t.insert(END, line)
self.update()
self.t.see(END)
And here is my non-threaded code (needs two functions to work)
def insertDump(self):
try:
data = self.dataQueue.get(block=False)
for line in data:
self.t.insert(END, line)
self.t.see(END)
self.update()
except:
print "error"
raise
def getDump(self):
self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
self.dataQueue.put(self.file)
This brings me to a design, as opposed to coding, question. The
non-threaded version seems to work just as well as the threaded one, in
terms of speed. Moreover, it is simpler to code and debug, because I
don't have to check to make sure the thread queue has data (I sometimes
get an 'Empty' error message when I first start the thread). Simply
using the Tk event loop (self.update) is also how I would have coded
this in Tcl.
So my question is this: under what circumstances in Python are threads
considered "best practice"? Am I wrong to use the Tk event loop instead
of threads?

D'oh, I got the code snippets mixed up:

non-threaded:

def insertDump(self):
self.finkinstalled = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
for line in self.finkinstalled:
self.t.insert(END, line)
self.update()
self.t.see(END)

threaded:

def insertDump(self):
try:
data = self.dataQueue.get(block=False)
for line in data:
self.t.insert(END, line)
self.t.see(END)
self.update()

except:
print "error"
raise

def getDump(self):

self.file = os.popen('/sw/bin/fink list', 'r', os.O_NONBLOCK)
self.dataQueue.put(self.file)

Sorry!
--
Kevin Walzer
Code by Kevinhttp://www.codebykevin.com
It looks like Tkinter is similar to wxPython in that you're not
supposed to use the mainloop for anything except the GUI and GUI
commands. The following websites have more info on Tkinter and
threads:

http://aspn.activestate.com/ASPN/Coo...n/Recipe/82965
http://www.thescripts.com/forum/thread22536.html
http://forums.devshed.com/python-pro...ds-123001.html

I use the Threading module for threading in wxPython. I think that
would probably serve you well with Tkinter as well. You can use the
join() method to wait for all the threads to exit.

Mike

Mar 27 '07 #3

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