My PyQt program has 2 widgets (selecting files etc) and then a Main Window which displays the results of the parsed files.
The program works great for small sample files, but when trying to parse larger files it will hang (display "Not Responding") and then show the results after about 30 seconds or so.
I would like to implement a QDialog before the Main Window opens. The QDialog will have a progress bar to let the user know when the Main Window will open.
This progress bar needs to be set to the length of time before the Main Window pops up.
What is the best way to implement this? I have seen some examples, but the progress bar is just set to a standardised time, not when the processing(parsing) is complete.
I currently have the following code which opens the Main Window.
def openWidgetMain(self):
self.WidgetMain = WidgetMain()
self.WidgetMain.show()
self.close()
All the processing for this window is done when it opens. So how do I connect the QProgressBar?
Put your long lasting process in some kind of thread. Read this: http://qt-project.org/doc/qt-5/threads-technologies.html
Emit a signal from that thread to update your progress bar. This way your application will not hang and the user sees the progress.
However it is up to your loading routine to decide which percentage to show in the progress bar. If you can't calculate an exact percentage try some kind of estimation (e.g. based on the size of the file vs. processed amount of the file).
First, best way to implement this, Your must estimate your load progress file. Next, implement it with QtCore.QThread to create background process. Last, put your call back progress into your QtGui.QMainWindow.
Little example;
import sys
import time
from PyQt4 import QtGui
from PyQt4 import QtCore
class QCustomThread (QtCore.QThread):
startLoad = QtCore.pyqtSignal(int)
progressLoad = QtCore.pyqtSignal(int)
statusLoad = QtCore.pyqtSignal(bool)
def __init__ (self, parentQWidget = None):
super(QCustomThread, self).__init__(parentQWidget)
self.wasCanceled = False
def run (self):
# Simulate data load estimation
numberOfprogress = 100
self.startLoad.emit(numberOfprogress)
for progress in range(numberOfprogress + 1):
# Delay
time.sleep(0.1)
if not self.wasCanceled:
self.progressLoad.emit(progress)
else:
break
self.statusLoad.emit(True if progress == numberOfprogress else False)
self.exit(0)
def cancel (self):
self.wasCanceled = True
class QCustomMainWindow (QtGui.QMainWindow):
def __init__ (self):
super(QCustomMainWindow, self).__init__()
# Create action with QPushButton
self.startQPushButton = QtGui.QPushButton('START')
self.startQPushButton.released.connect(self.startWork)
self.setCentralWidget(self.startQPushButton)
# Create QProgressDialog
self.loadingQProgressDialog = QtGui.QProgressDialog(self)
self.loadingQProgressDialog.setLabelText('Loading')
self.loadingQProgressDialog.setCancelButtonText('Cancel')
self.loadingQProgressDialog.setWindowModality(QtCore.Qt.WindowModal)
def startWork (self):
myQCustomThread = QCustomThread(self)
def startLoadCallBack (numberOfprogress):
self.loadingQProgressDialog.setMinimum(0)
self.loadingQProgressDialog.setMaximum(numberOfprogress)
self.loadingQProgressDialog.show()
def progressLoadCallBack (progress):
self.loadingQProgressDialog.setValue(progress)
def statusLoadCallBack (flag):
print 'SUCCESSFUL' if flag else 'FAILED'
myQCustomThread.startLoad.connect(startLoadCallBack)
myQCustomThread.progressLoad.connect(progressLoadCallBack)
myQCustomThread.statusLoad.connect(statusLoadCallBack)
self.loadingQProgressDialog.canceled.connect(myQCustomThread.cancel)
myQCustomThread.start()
myQApplication = QtGui.QApplication(sys.argv)
myQCustomMainWindow = QCustomMainWindow()
myQCustomMainWindow.show()
sys.exit(myQApplication.exec_())
More infomation of QtCore.QThread (Recommend read to understand behavior)
Related
This question already has an answer here:
Progress Bar Does not Render Until Job is Complete
(1 answer)
Closed 2 years ago.
I am using PyQt5 to write an app that manages Sales Orders. When creating an Order or deleting itI want to display a marqee style progress dialog to indicate that the app is working. I have visited a lot of posts where the answer involved using QThread.I have tried to implement it but it seems I am missing something. This is my threading class.
class Worker(QThread):
finished = Signal()
def run(self):
self.x = QProgressDialog("Please wait..",None,0,0)
self.x.show()
def stop(self):
self.x.close()
In the Main window's init I create self.worker=Worker()
Now the code for deleting an entry is for example:
msg = MsgBox("yn", "Delete Order", "Are you sure you want to delete this order?") # Wrapper for the QMessageBox
if msg == 16384:
self.worker.start() ## start the worker thread, hoping to start the progress dialog
session.delete(order) ##delete order from db
session.commit() ##commit to db
self.change_view("Active", 8) ##func. clean up the table.
self.worker.finished.emit() ##emit the finished signal to close the progress dialog
The result is no progress dialog being displayed. The gui just freezes for a second or two and then the entry deletes without any progress dialog being displayed.
Sorry my code is quite long so I couldn't include it all here, I just wanted to see if I got something terribly wrong.
There are two main problems with your code:
GUI elements (everything inherited or related to a QWidget subclass) must be created and accessed only from the main Qt thread.
assuming that what takes some amount of time is the delete/commit operations, it's those operation that must go in the thread while showing the progress dialog from the main thread, not the other way around.
Also, consider that QThread already has a finished() signal, and you should not overwrite it.
This is an example based on your code:
class Worker(QThread):
def __init__(self, session, order):
super.__init__()
self.session = session
self.order = order
def run(self):
self.session.delete(self.order)
self.session.commit()
class Whatever(QMainWindow):
def __init__(self):
super().__init__()
# ...
self.progressDialog = QProgressDialog("Please wait..", None, 0, 0, self)
def deleteOrder(self, session, order):
msg = MsgBox("yn", "Delete Order",
"Are you sure you want to delete this order?")
if msg == MsgBox.Yes: # you should prefer QMessageBox flags
self.worker = Worker(session, order)
self.worker.started(self.progressDialog.show())
self.worker.finished(self.deleteCompleted)
self.worker.start()
def deleteCompleted(self):
self.progressDialog.hide()
self.change_view("Active", 8)
Since the progress dialog should stay open while processing, you should also prevent the user to be able to close it. To do that you can install an event filter on it and ensure that any close event gets accepted; also, since QProgressDialog inherits from QDialog, the Esc key should be filtered out, otherwise it will not close the dialog, but would reject and hide it.
class Whatever(QMainWindow):
def __init__(self):
super().__init__()
# ...
self.progressDialog = QProgressDialog("Please wait..", None, 0, 0, self)
self.progressDialog.installEventFilter(self)
def eventFilter(self, source, event):
if source == self.progressDialog:
# check for both the CloseEvent *and* the escape key press
if event.type() == QEvent.Close or event == QKeySequence.Cancel:
event.accept()
return True
return super().eventFilter(source, event)
Windows 10 with Python 2.7.13 (32 bit)
I have a Python tkinter program with a progress bar. The program performs a long-running operation, and then waits for a set amount of time before repeating it.
To provide feedback to the user, a progress bar is updated in derterminate mode when counting down to the next operation, and then switches to an indeterminate bar during the operation (of unknown duration).
After 15-30mins, during a countdown using the code below, Windows pops up a python.exe has stopped working dialog, offering only the option to close the program, and the program is unresponsive (presumably because Windows has halted it).
I cannot figure out why this is occurring. During this time, in the GUI the following segment of code is running:
def wait_nextop(self, delay):
end = time.time() + delay
self.progress_bar.stop()
self.progress_bar.config(mode = 'determinate', max = delay)
while time.time() < end:
remaining = (end - time.time()) + 1
self.progress_bar.config(value = (delay - remaining))
remaining_text = str(datetime.timedelta(seconds = int(remaining)))
self.progress_text.config(text = 'Next operation in ' + remaining_text)
time.sleep(0.1)
self.progress_text.config(text = 'Operation in progress')
self.progress_bar.config(mode = 'indeterminate')
self.progress_bar.start()
In this, delay is an integer delay in seconds. self.progress_bar is an instance of ttk.ProgressBar and self.progress_text is an instance of tkinter.Label. time and datetime are from the standard libraries.
Python offers no stack trace, and I do not currently have other systems available to test this on. It should be noted that this GUI function is called by another thread, but is intended to execute within the main thread.
I've seen these similar questions, but couldn't find a working resolution:
Python tkinter code stops working
Tkinter python crashes on new thread trying to log on main thread
Based on advice from the comments, it seems that I should be using tkinter's events system, rather than calling functions in the GUI thread directly.
Here is a working example for Python2.7 using the described concepts. It creates the GUI with progress bar, and then updates it from another thread using the event system.
## Import the required modules
import threading
import Tkinter as tk
import ttk
import time
import random
## Class for creating the GUI
class GUI():
def __init__(self):
## Make the GUI
self.root = tk.Tk()
self.progress = ttk.Progressbar(self.root, orient = 'horizontal', length = 100, mode = 'determinate', max = 10)
## Bind an event to trigger the update
self.root.bind('<<MoveIt>>', self.update_progress)
## Pack the progress bar in to the GUI
self.progress.pack()
def run(self):
## Enter the main GUI loop. this blocks the main thread
self.root.mainloop()
## Updates the progress bar
def update_progress(self, event):
## Work out what the new value will be
new_value = self.progress['value'] + 1
## If the new value is less than 10..
if new_value < 10:
print('[main thread] New progress bar value is ' + str(new_value))
## Update the progress bar value
self.progress.config(value = new_value)
## Force the GUI to update
self.root.update()
## If the new value is more than 10
else:
print('[main thread] Progress bar done. Exiting!')
## Exit the GUI (and terminate the script)
self.root.destroy()
## Class for creating the worker thread
class Worker(threading.Thread):
def __init__(self, ui):
## Run the __init__ function from our threading.Thread parent
threading.Thread.__init__(self)
## Save a local reference to the GUI object
self.ui = ui
## Set as a daemon so we don't block the program from exiting
self.setDaemon(True)
def run(self):
print('[new thread] starting')
## Count to 10
for i in range(10):
## Generate an event to trigger the progress bar update
ui.root.event_generate('<<MoveIt>>', when = 'tail')
## Wait between one and three seconds before doing it again
wait = random.randint(1,3)
print('[new thread] Incrementing progress bar again in ' + str(wait) + ' seconds')
time.sleep(wait)
## Create an instance of the GUI class
ui = GUI()
## Create an instance of the Worker class and tell it about the GUI object
work = Worker(ui)
## Start the worker thread
work.start()
## Start the GUI thread (blocking)
ui.run()
I'm writing a program with a GUI using TKinter, in which the user can click a button and a new process is started to perform work using multiprocess.Process. This is necessary so the GUI can still be used while the work is being done, which can take several seconds.
The GUI also has a text box where the status of the program is displayed when things happen. This is often straight forward, with each function calling an add_text() function which just prints text in the text box. However, when add_text() is called in the separate process, the text does not end up in the text box.
I've thought about using a Pipe or Queue, but that would require using some sort of loop to check if anything has been returned from the process and that would also cause the main (GUI) process to be unusable. Is there some way to call a function in one process that will do work in another?
Here's an simple example of what I'm trying to do
import time
import multiprocessing as mp
import tkinter as tk
textbox = tk.Text()
def add_text(text):
# Insert text into textbox
textbox.insert(tk.END, text)
def worker():
x = 0
while x < 10:
add_text('Sleeping for {0} seconds'.format(x)
x += 1
time.sleep(1)
proc = mp.Process(target=worker)
# Usually happens on a button click
proc.start()
# GUI should still be usable here
The asyncronous things actually require loop.
You could attach function to the TkInter's loop by using Tk.after() method.
import Tkinter as tk
class App():
def __init__(self):
self.root = tk.Tk()
self.check_processes()
self.root.mainloop()
def check_processes(self):
if process_finished:
do_something()
else:
do_something_else()
self.after(1000, check_processes)
app=App()
I ended up using a multiprocessing.Pipe by using TKinter's after() method to perform the looping. It loops on an interval and checks the pipe to see if there's any messages from the thread, and if so it inserts them into the text box.
import tkinter
import multiprocessing
def do_something(child_conn):
while True:
child_conn.send('Status text\n')
class Window:
def __init__(self):
self.root = tkinter.Tk()
self.textbox = tkinter.Text()
self.parent_conn, child_conn = multiprocessing.Pipe()
self.process = multiprocessing.Process(target=do_something, args=(child_conn,))
def start(self):
self.get_status_updates()
self.process.start()
self.root.mainloop()
def get_status_updates()
status = self.check_pipe()
if status:
self.textbox.add_text(status)
self.root.after(500, self.get_status_updates) # loop every 500ms
def check_pipe():
if self.parent_conn.poll():
status = self.parent_conn.recv()
return status
return None
I have a GUI in PyQt with a function addImage(image_path). Easy to imagine, it is called when a new image should be added into a QListWidget. For the detection of new images in a folder, I use a threading.Thread with watchdog to detect file changes in the folder, and this thread then calls addImage directly.
This yields the warning that QPixmap shouldn't be called outside the gui thread, for reasons of thread safety.
What is the best and most simple way to make this threadsafe? QThread? Signal / Slot? QMetaObject.invokeMethod? I only need to pass a string from the thread to addImage.
You should use the built in QThread provided by Qt. You can place your file monitoring code inside a worker class that inherits from QObject so that it can use the Qt Signal/Slot system to pass messages between threads.
class FileMonitor(QObject):
image_signal = QtCore.pyqtSignal(str)
#QtCore.pyqtSlot()
def monitor_images(self):
# I'm guessing this is an infinite while loop that monitors files
while True:
if file_has_changed:
self.image_signal.emit('/path/to/image/file.jpg')
class MyWidget(QtGui.QWidget):
def __init__(self, ...)
...
self.file_monitor = FileMonitor()
self.thread = QtCore.QThread(self)
self.file_monitor.image_signal.connect(self.image_callback)
self.file_monitor.moveToThread(self.thread)
self.thread.started.connect(self.file_monitor.monitor_images)
self.thread.start()
#QtCore.pyqtSlot(str)
def image_callback(self, filepath):
pixmap = QtGui.QPixmap(filepath)
...
I believe the best approach is using the signal/slot mechanism. Here is an example. (Note: see the EDIT below that points out a possible weakness in my approach).
from PyQt4 import QtGui
from PyQt4 import QtCore
# Create the class 'Communicate'. The instance
# from this class shall be used later on for the
# signal/slot mechanism.
class Communicate(QtCore.QObject):
myGUI_signal = QtCore.pyqtSignal(str)
''' End class '''
# Define the function 'myThread'. This function is the so-called
# 'target function' when you create and start your new Thread.
# In other words, this is the function that will run in your new thread.
# 'myThread' expects one argument: the callback function name. That should
# be a function inside your GUI.
def myThread(callbackFunc):
# Setup the signal-slot mechanism.
mySrc = Communicate()
mySrc.myGUI_signal.connect(callbackFunc)
# Endless loop. You typically want the thread
# to run forever.
while(True):
# Do something useful here.
msgForGui = 'This is a message to send to the GUI'
mySrc.myGUI_signal.emit(msgForGui)
# So now the 'callbackFunc' is called, and is fed with 'msgForGui'
# as parameter. That is what you want. You just sent a message to
# your GUI application! - Note: I suppose here that 'callbackFunc'
# is one of the functions in your GUI.
# This procedure is thread safe.
''' End while '''
''' End myThread '''
In your GUI application code, you should create the new Thread, give it the right callback function, and make it run.
from PyQt4 import QtGui
from PyQt4 import QtCore
import sys
import os
# This is the main window from my GUI
class CustomMainWindow(QtGui.QMainWindow):
def __init__(self):
super(CustomMainWindow, self).__init__()
self.setGeometry(300, 300, 2500, 1500)
self.setWindowTitle("my first window")
# ...
self.startTheThread()
''''''
def theCallbackFunc(self, msg):
print('the thread has sent this message to the GUI:')
print(msg)
print('---------')
''''''
def startTheThread(self):
# Create the new thread. The target function is 'myThread'. The
# function we created in the beginning.
t = threading.Thread(name = 'myThread', target = myThread, args = (self.theCallbackFunc))
t.start()
''''''
''' End CustomMainWindow '''
# This is the startup code.
if __name__== '__main__':
app = QtGui.QApplication(sys.argv)
QtGui.QApplication.setStyle(QtGui.QStyleFactory.create('Plastique'))
myGUI = CustomMainWindow()
sys.exit(app.exec_())
''' End Main '''
EDIT
Mr. three_pineapples and Mr. Brendan Abel pointed out a weakness in my approach. Indeed, the approach works fine for this particular case, because you generate / emit the signal directly. When you deal with built-in Qt signals on buttons and widgets, you should take another approach (as specified in the answer of Mr. Brendan Abel).
Mr. three_pineapples adviced me to start a new topic in StackOverflow to make a comparison between the several approaches of thread-safe communication with a GUI. I will dig into the matter, and do that tomorrow :-)
I'm trying to code something that downloads a file from a webserver and saves it, showing the download progress in a QProgressBar.
Now, there are ways to do this in regular Python and it's easy. Problem is that it locks the refresh of the progressBar. Solution is to use PyQT's QNetworkManager class. I can download stuff just fine with it, I just can't get the setup to show the progress on the progressBar. Here´s an example:
class Form(QDialog):
def __init__(self,parent=None):
super(Form,self).__init__(parent)
self.progressBar = QProgressBar()
self.reply = None
layout = QHBoxLayout()
layout.addWidget(self.progressBar)
self.setLayout(layout)
self.manager = QNetworkAccessManager(self)
self.connect(self.manager,SIGNAL("finished(QNetworkReply*)"),self.replyFinished)
self.Down()
def Down(self):
address = QUrl("http://stackoverflow.com") #URL from the remote file.
self.manager.get(QNetworkRequest(address))
def replyFinished(self, reply):
self.connect(reply,SIGNAL("downloadProgress(int,int)"),self.progressBar, SLOT("setValue(int)"))
self.reply = reply
self.progressBar.setMaximum(reply.size())
alltext = self.reply.readAll()
#print alltext
#print alltext
def updateBar(self, read,total):
print "read", read
print "total",total
#self.progressBar.setMinimum(0)
#self.progressBar.setMask(total)
#self.progressBar.setValue(read)
In this case, my method "updateBar" is never called... any ideas?
Well you haven't connected any of the signals to your updateBar() method.
change
def replyFinished(self, reply):
self.connect(reply,SIGNAL("downloadProgress(int,int)"),self.progressBar, SLOT("setValue(int)"))
to
def replyFinished(self, reply):
self.connect(reply,SIGNAL("downloadProgress(int,int)"),self.updateBar)
Note that in Python you don't have to explicitly use the SLOT() syntax; you can just pass the reference to your method or function.
Update:
I just wanted to point out that if you want to use a Progress bar in any situation where your GUI locks up during processing, one solution is to run your processing code in another thread so your GUI receives repaint events. Consider reading about the QThread class, in case you come across another reason for a progress bar that does not have a pre-built solution for you.