I am writing a Python 3.9 GUI application using wxPython. The application allows the user to enter information and press a "calculate" button. This will kick of a long running thread that updates the main application window with status updates. The application successfully kicks off the calculation thread and remains responsive.
Now I would like to add an "abort" button that will stop/cancel/abort the previously started thread when the users chooses to press the "abort" button.
After looking for some time, I found the code below on the wxPython website that has the general framework I am looking for. It follows the main logic of my application in a more simple form. It is missing the ongoing GUI status update, so I made a single addition to simulate the GUI status updates - see "<<<<<<" reference in the code below.
wx.PostEvent(self._notify_window, ResultEvent(i))
However, after adding this line it seems to break the event handling when the user is pressing the "stop" button while the processing thread has started. When pressing the "stop" button after 3-4 seconds, the counting thread in the sample code below continues to run and is ignoring the "stop" button event.
When this line is removed, the "stop" feature in the example code below works and the loop is disrupted.
How can I keep the feature of updating the GUI with status updates while the counting thread is running and also have the "stop" button terminate the actively running thread?
I am sure there are ways to optimize the code below. Please don't hesitate to share your thoughts/knowledge. Thank you.
import time
from threading import *
import wx
# Button definitions
ID_START = wx.NewId()
ID_STOP = wx.NewId()
# Define notification event for thread completion
EVT_RESULT_ID = wx.NewId()
def EVT_RESULT(win, func):
"""Define Result Event."""
win.Connect(-1, -1, EVT_RESULT_ID, func)
class ResultEvent(wx.PyEvent):
"""Simple event to carry arbitrary result data."""
def __init__(self, data):
"""Init Result Event."""
wx.PyEvent.__init__(self)
self.SetEventType(EVT_RESULT_ID)
self.data = data
# Thread class that executes processing
class WorkerThread(Thread):
"""Worker Thread Class."""
def __init__(self, notify_window):
"""Init Worker Thread Class."""
Thread.__init__(self)
self._notify_window = notify_window
self._want_abort = 0
# This starts the thread running on creation, but you could
# also make the GUI thread responsible for calling this
#self.start()
def run(self):
"""Run Worker Thread."""
# This is the code executing in the new thread. Simulation of
# a long process (well, 10s here) as a simple loop - you will
# need to structure your processing so that you periodically
# peek at the abort variable
for i in range(10):
if self._want_abort:
# Use a result of None to acknowledge the abort (of
# course you can use whatever you'd like or even
# a separate event type)
wx.PostEvent(self._notify_window, ResultEvent(None))
return
time.sleep(2)
wx.PostEvent(self._notify_window, ResultEvent(i)) <<<<<<< Added to simulate "status update" feedback of my application.
# Here's where the result would be returned (this is an
# example fixed result of the number 10, but it could be
# any Python object)
wx.PostEvent(self._notify_window, ResultEvent(10))
def abort(self):
"""abort worker thread."""
# Method for use by main thread to signal an abort
self._want_abort = 1
# GUI Frame class that spins off the worker thread
class MainFrame(wx.Frame):
"""Class MainFrame."""
def __init__(self, parent, id):
"""Create the MainFrame."""
wx.Frame.__init__(self, parent, id, 'Thread Test')
# Dumb sample frame with two buttons
wx.Button(self, ID_START, 'Start', pos=(0,0))
wx.Button(self, ID_STOP, 'Stop', pos=(0,50))
self.status = wx.StaticText(self, -1, '', pos=(0,100))
self.Bind(wx.EVT_BUTTON, self.OnStart, id=ID_START)
self.Bind(wx.EVT_BUTTON, self.OnStop, id=ID_STOP)
# Set up event handler for any worker thread results
EVT_RESULT(self,self.OnResult)
# And indicate we don't have a worker thread yet
self.worker = None
def OnStart(self, event):
"""Start Computation."""
# Trigger the worker thread unless it's already busy
if not self.worker:
self.status.SetLabel('Starting computation')
self.worker = WorkerThread(self)
self.worker.start()
def OnStop(self, event):
"""Stop Computation."""
# Flag the worker thread to stop if running
if self.worker:
self.status.SetLabel('Trying to abort computation')
self.worker.abort()
def OnResult(self, event):
"""Show Result status."""
if event.data is None:
# Thread aborted (using our convention of None return)
self.status.SetLabel('Computation aborted')
else:
# Process results here
self.status.SetLabel('Computation Result: %s' % event.data)
# In either event, the worker is done
self.worker = None
class MainApp(wx.App):
"""Class Main App."""
def OnInit(self):
"""Init Main App."""
self.frame = MainFrame(None, -1)
self.frame.Show(True)
self.SetTopWindow(self.frame)
return True
if __name__ == '__main__':
app = MainApp(0)
app.MainLoop()
CodePudding user response：
You are simply setting self.worker = None at the wrong point.
It should only be set to None on Stop or when it terminates naturally, other than that the code is fine.
e.g.
import time
from threading import *
import wx
# Button definitions
ID_START = wx.NewId()
ID_STOP = wx.NewId()
# Define notification event for thread completion
EVT_RESULT_ID = wx.NewId()
def EVT_RESULT(win, func):
"""Define Result Event."""
win.Connect(-1, -1, EVT_RESULT_ID, func)
class ResultEvent(wx.PyEvent):
"""Simple event to carry arbitrary result data."""
def __init__(self, data):
"""Init Result Event."""
wx.PyEvent.__init__(self)
self.SetEventType(EVT_RESULT_ID)
self.data = data
# Thread class that executes processing
class WorkerThread(Thread):
"""Worker Thread Class."""
def __init__(self, notify_window):
"""Init Worker Thread Class."""
Thread.__init__(self)
self._notify_window = notify_window
self._want_abort = 0
# This starts the thread running on creation, but you could
# also make the GUI thread responsible for calling this
#self.start()
def run(self):
"""Run Worker Thread."""
# This is the code executing in the new thread. Simulation of
# a long process (well, 10s here) as a simple loop - you will
# need to structure your processing so that you periodically
# peek at the abort variable
for i in range(10):
if self._want_abort:
# Use a result of None to acknowledge the abort (of
# course you can use whatever you'd like or even
# a separate event type)
wx.PostEvent(self._notify_window, ResultEvent(None))
return
time.sleep(1)
wx.PostEvent(self._notify_window, ResultEvent(i)) # <<<<<<< Added to simulate "status update" feedback of my application.
# Here's where the result would be returned (this is an
# example fixed result of the number 10, but it could be
# any Python object)
time.sleep(2)
wx.PostEvent(self._notify_window, ResultEvent(10))
def abort(self):
"""abort worker thread."""
# Method for use by main thread to signal an abort
self._want_abort = 1
# GUI Frame class that spins off the worker thread
class MainFrame(wx.Frame):
"""Class MainFrame."""
def __init__(self, parent, id):
"""Create the MainFrame."""
wx.Frame.__init__(self, parent, id, 'Thread Test')
# Dumb sample frame with two buttons
wx.Button(self, ID_START, 'Start', pos=(0,0))
wx.Button(self, ID_STOP, 'Stop', pos=(0,50))
self.status = wx.StaticText(self, -1, '', pos=(0,100))
self.Bind(wx.EVT_BUTTON, self.OnStart, id=ID_START)
self.Bind(wx.EVT_BUTTON, self.OnStop, id=ID_STOP)
# Set up event handler for any worker thread results
EVT_RESULT(self,self.OnResult)
# And indicate we don't have a worker thread yet
self.worker = None
def OnStart(self, event):
"""Start Computation."""
# Trigger the worker thread unless it's already busy
if self.worker:
return
else:
self.status.SetLabel('Starting computation')
self.worker = WorkerThread(self)
self.worker.start()
self.status.SetLabel('Computation started')
def OnStop(self, event):
"""Stop Computation."""
# Flag the worker thread to stop if running
if self.worker:
self.status.SetLabel('Trying to abort computation')
self.worker.abort()
self.worker = None
else:
self.status.SetLabel('Computation not running')
def OnResult(self, event):
"""Show Result status."""
if event.data is None:
# Thread aborted (using our convention of None return)
self.status.SetLabel('Computation aborted')
else:
# Process results here
self.status.SetLabel('Computation Result: %s' % event.data)
if event.data == 10:
self.worker = None
self.status.SetLabel('Computation Finished')
class MainApp(wx.App):
"""Class Main App."""
def OnInit(self):
"""Init Main App."""
self.frame = MainFrame(None, -1)
self.frame.Show(True)
self.SetTopWindow(self.frame)
return True
if __name__ == '__main__':
app = MainApp(0)
app.MainLoop()