Using PyQt5, I want to implement a two windows displaying one after another automatically, without the user interacting with any window. Something like this:
While True:
Show Window1
wait 2 seconds
Close Window1
Show Window2
wait 2 seconds
Close Window2
The problem I am having is that the main UI thread is stuck in app.exec_() function, so it cannot implement the opening and closing logic.
import sys
from PyQt5.QtWidgets import *
from PyQt5 import uic
class Win1(QMainWindow):
def __init__(self):
super(Win1, self).__init__()
uic.loadUi('win1.ui', self)
self.show()
class Win2(QMainWindow):
def __init__(self):
super(Win2, self).__init__()
uic.loadUi('win2.ui', self)
self.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
while True:
win = Win1()
time.sleep(1)
win.close()
win = Win2()
time.sleep(1)
win.close()
app.exec_() # <--------- Program blocks here
I would appreciate if someone can share a minimal example for this working without blocking. Or please point to the mechanism that should be used.
If you are going to work with Qt then you should forget about sequential logic but you have to implement the logic using events. For example, in your case you want one window to be shown every time T and another to be hidden, so that can be implemented with a QTimer and a flag:
import sys
from PyQt5.QtCore import QTimer
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5 import uic
class Win1(QMainWindow):
def __init__(self):
super(Win1, self).__init__()
uic.loadUi('win1.ui', self)
self.show()
class Win2(QMainWindow):
def __init__(self):
super(Win2, self).__init__()
uic.loadUi('win2.ui', self)
self.show()
if __name__ == "__main__":
app = QApplication(sys.argv)
timer = QTimer()
timer.setProperty("flag", True)
win1 = Win1()
win2 = Win2()
def on_timeout():
flag = timer.property("flag")
if flag:
win1.show()
win2.close()
else:
win2.show()
win1.close()
timer.setProperty("flag", not flag)
timer.timeout.connect(on_timeout)
timer.start(1 * 1000)
on_timeout()
app.exec_()
You should not use while loop or time.sleep since they block the eventloop in which the GUI lives, that is: they freeze the windows
Related
I'm creating a PyQt app where I want to have a background thread that connects some event handlers and then loops forever until the main window is closed. The problem I am experiencing is that the event handlers I am connecting only work if they are functions defined inside my MainWindow class. I have created a minimal repro below:
import threading
from PyQt5.QtWidgets import QApplication, QDialog, QPushButton, QVBoxLayout
class MainWindow(QDialog):
def __init__(self):
super(MainWindow, self).__init__()
self.button1 = QPushButton("Click Me", self)
self.button2 = QPushButton("Me Too!", self)
layout = QVBoxLayout()
layout.addWidget(self.button1)
layout.addWidget(self.button2)
self.setLayout(layout)
def test(self):
print("test inside class")
def test2():
print("test outside class")
def main(window):
window.button1.clicked.connect(window.test)
window.button2.clicked.connect(test2)
# Loop that runs in thread...
app = QApplication([])
window = MainWindow()
window.show()
threading.Thread(target=main, args=[window]).start()
app.exec_()
When I run this code, the first button prints a message to the console as expected, but the second one does nothing when clicked. If I run the main(window) function in the main thread, then both buttons work. I'm aware that in my small sample program this would be the obvious solution, but for reasons that are complex to explain I need to be able to connect the event handlers from the background thread in my application. Why does connecting a function like test2() that is defined outside the MainWindow class not work when I do it outside of the main thread?
I'm still finding out the reason for the problem but the solution is to indicate the type of connection, in this case Qt::DirectConnection that will make the function test2 run on the same thread of the object that emits the signal (the object that emits the signal is the button that lives in the main thread).
import threading
from PyQt5 import QtCore, QtWidgets
class MainWindow(QtWidgets.QDialog):
def __init__(self):
super(MainWindow, self).__init__()
self.button1 = QtWidgets.QPushButton("Click Me")
self.button2 = QtWidgets.QPushButton("Me Too!")
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(self.button1)
layout.addWidget(self.button2)
#QtCore.pyqtSlot()
def test(self):
print("test inside class")
def test2():
print("test outside class")
def main(window):
window.button1.clicked.connect(window.test)
window.button2.clicked.connect(test2, QtCore.Qt.DirectConnection)
while True:
QtCore.QThread.sleep(1)
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
window = MainWindow()
window.show()
threading.Thread(target=main, args=(window,), daemon=True).start()
sys.exit(app.exec_())
import sys
from PySide2.QtCore import QFile
from PySide2.QtWidgets import QApplication, QMainWindow
from PySide2.QtUiTools import QUiLoader
class MyMainWindow(QMainWindow):
def __init__(self):
super().__init__()
loader = QUiLoader()
self.ui = loader.load("mainWindow.ui", self)
self.ui.pushButton_call_dialog.clicked.connect(self.call_dialog)
self.ui.close()
self.ui.show()
def call_dialog(self):
loader = QUiLoader()
self.dialog = loader.load("dialog.ui")
self.dialog.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
window = MyMainWindow()
window.show
sys.exit(app.exec_())
Hi everyone,
any idea why the second (dialog) window closes the entire application?
Of course, it is not a crash since i'm getting a message saying:
Process finished with exit code 0
Thanks for your help
You could handle your QDialog on a separate class, and then make them interact only, the structure might change a bit, but you can see if it's a viable answer:
import sys
from PySide2.QtWidgets import *
class MyWindow(QMainWindow):
def __init__(self):
QMainWindow.__init__(self)
button = QPushButton("Dialog")
button.clicked.connect(self.open_dialog)
self.setCentralWidget(button)
def open_dialog(self):
dialog = MyDialog()
dialog.show()
dialog.exec_()
class MyDialog(QDialog):
def __init__(self):
QDialog.__init__(self)
button = QPushButton("Close")
button.clicked.connect(self.close_dialog)
layout = QHBoxLayout()
layout.addWidget(button)
self.setLayout(layout)
def close_dialog(self):
self.close()
if __name__ == "__main__":
app = QApplication()
m = MyWindow()
m.show()
sys.exit(app.exec_())
Just notice that you should include the setUp step on each class.
Hope it helps.
To put the dialog into a separate class didn't work for either.
Every time the Dialog.close() event was called, it closes the whole application.
What worked for me, was to use hide() instead
I would like to call a function after the GUI displays. If I run function in init it prevents gui from displaying until after it is completed.
class MyApp(QtWidgets.QMainWindow, Ui_MainWindow):
def __init__(self):
QtWidgets.QMainWindow.__init__(self)
Ui_MainWindow.__init__(self)
self.setupUi(self)
self.function() #waits for this to finish until gui displayed
def function(self):
self.guiBox.setValue(initData)
#inits stuff, takes 5 seconds
The function initializes a piece of equipment via serial port... It takes s few seconds, and it takes gui attributes and updates gui display boxes.
Add single shot timer 1 ms and after call function
class MyApp(QtWidgets.QMainWindow, Ui_MainWindow):
def __init__(self):
QtWidgets.QMainWindow.__init__(self)
Ui_MainWindow.__init__(self)
self.setupUi(self)
QTimer.singleShot(1,self.function) #waits for this to finish until gui displayed
def function(self):
self.guiBox.setValue(initData)
#inits stuff, takes 5 seconds
Time-consuming tasks are blocking, and this goes against the natural way of working on the GUI, an option is to use qApp.processEvents(), for example:
def function(self):
self.guiBox.setValue(initData)
code1
QtWidgets.qApp.processEvents()
code2
QtWidgets.qApp.processEvents()
...
I would recommend QThreads, especially if you are performing a ton of other actions in your "function." This example isn't the only way to thread in PyQt, but thought an example where you are able to pass data back and forth between the thread and the main gui would be best.
import os
import sys
from PyQt5.QtWidgets import QApplication, QVBoxLayout, QWidget
from PyQt5.QtCore import QUrl, QEventLoop, QThread, QObject, pyqtSlot, pyqtSignal
from PyQt5.QtWebEngineWidgets import QWebEngineView
class time_consuming_function(QObject):
def __init__(self, widget):
super(time_consuming_function, self).__init__()
self.widget = widget
self.run_trigger.connect(self.run)
run_trigger = pyqtSignal(int, int)
#pyqtSlot(int, int)
def run(self, int1, int2):
print("In Time Consuming Function")
for i in range(100000000):
i*i
print("Finished with Time Consuming Function")
self.widget.someTrigger.emit([1, 2, 3])
class WebPage(QWebEngineView):
def __init__(self):
QWebEngineView.__init__(self)
self.load(QUrl("https://www.google.com"))
self.loadFinished.connect(self._on_load_finished)
self.someTrigger.connect(self.gui_response)
self.thread = QThread()
self.thread.start()
self.consume = time_consuming_function(self)
self.consume.moveToThread(self.thread)
self.consume.run_trigger.emit(1,1)
someTrigger = pyqtSignal(list)
def _on_load_finished(self):
print("Finished Loading")
def gui_response(self, data):
print("Responding to GUI: ", str(data))
if __name__ == "__main__":
app = QApplication(sys.argv)
web = WebPage()
web.show()
sys.exit(app.exec_())
I'd say the easiest way without using thread and related would be to verify if the last event of showing up the window was executed and then call your method.
You'd have something like that:
import sys
from PyQt5.QtCore import QEvent
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWidgets import QMainWindow
class MainWindow(QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.setFixedSize(500, 500)
self.move(300, 50)
def print_1_bi(self):
for i in range(10**9): print(i)
def event(self, event):
if event.type() == QEvent.InputMethodQuery:
self.print_1_bi()
return super(MainWindow, self).event(event)
if __name__ == "__main__":
app = QApplication(sys.argv)
mw = MainWindow()
mw.show()
sys.exit(app.exec_())
Note: Remember that even though the UI already showed up your application will be waiting your method to finish, if it's a problem you'll have to use process like the guys told you to in the other answers.
How to call a method asynchronously in PyQt5 using Python3?
I have tried to use a signal to do it.
import sys
from time import sleep
from PyQt5.QtCore import pyqtSignal
from PyQt5.QtWidgets import QApplication, QMainWindow, QLabel
class MainWindow(QMainWindow):
asyncFuncSignal = pyqtSignal()
def __init__(self):
super().__init__()
self.initUi()
def initUi(self):
self.label = QLabel(self)
self.label.setText("loading...")
# Trying to call 'self.asyncFunc' asynchronously
self.asyncFuncSignal.connect(self.asyncFunc)
self.asyncFuncSignal.emit()
print("loaded")
def asyncFunc(self):
# Doing something hard that takes time
# I have used 'sleep' to implement the delay
sleep(2)
self.label.setText("done")
print("asyncFunc finished")
if __name__ == "__main__":
app = QApplication(sys.argv)
window = MainWindow()
window.show()
sys.exit(app.exec_())
This program tries to finish asyncFunc before writing "loaded". But I would like the program to finish initUi immediately with shown loading... in the label and after that the text done appears in 2 seconds.
What is the best and the shortest way to do it?
It's said here http://pyqt.sourceforge.net/Docs/PyQt5/signals_slots.html I can use queued connections but I haven't found an example how to implement it.
PyQt5.QtCore.Qt.QueuedConnection may help. Just replace
self.asyncFuncSignal.connect(self.asyncFunc)
with
from PyQt5.QtCore import Qt
...
self.asyncFuncSignal.connect(self.asyncFunc, Qt.QueuedConnection)
I am having problems showing a QWidget window for the user to input some data.
My script has not GUI, but I just want to show this small QWidget window.
I created the window with QtDesigner, and now I am trying to show the QWidget window like this:
from PyQt4 import QtGui
from input_data_window import Ui_Form
class childInputData(QtGui.QWidget ):
def __init__(self, parent=None):
super(childInputData, self).__init__()
self.ui = Ui_Form()
self.ui.setupUi(self)
self.setFocus(True)
self.show()
And then, from my main class, I am doing like that:
class myMainClass():
childWindow = childInputData()
That gave me the error:
QWidget: Must construct a QApplication before a QPaintDevice
So now I am doing, from my main class:
class myMainClass():
app = QtGui.QApplication(sys.argv)
childWindow = childInputData()
Now there is no error, but the window is showed twice and the script does not wait until the data is entered, it just shows the window and continues without waiting.
What is wrong here?
It's perfectly normal that the window is shown and the script goes on: you never told the script to wait for the user to answer. You just told it to show a window.
What you would like is the script to stop until the user is done and the window is closed.
Here's one way to do it:
from PyQt4 import QtGui,QtCore
import sys
class childInputData(QtGui.QWidget):
def __init__(self, parent=None):
super(childInputData, self).__init__()
self.show()
class mainClass():
def __init__(self):
app=QtGui.QApplication(sys.argv)
win=childInputData()
print("this will print even if the window is not closed")
app.exec_()
print("this will be print after the window is closed")
if __name__ == "__main__":
m=mainClass()
The exec() method "Enters the main event loop and waits until exit() is called" (doc):
the script will be blocked on the line app.exec_() until the window is closed.
NB: using sys.exit(app.exec_()) would cause the script to end when the window is closed.
An other way is to use QDialog instead of QWidget. You then replace self.show() by self.exec(), which will block the script
From the doc:
int QDialog::exec()
Shows the dialog as a modal dialog, blocking until the user closes it
Finally, this answer of a related question advocates not to use exec, but to set the window modality with win.setWindowModality(QtCore.Qt.ApplicationModal). However this doesn't work here: it blocks inputs in other windows, but do not block the script.
you dont need the myMainClass...do something like this:
import sys
from PyQt4 import QtGui
from input_data_window import Ui_Form
class childInputData(QtGui.QWidget):
def __init__(self, parent=None):
super(childInputData, self).__init__(parent)
self.ui = Ui_Form()
self.ui.setupUi(self)
self.setFocus(True)
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
win = childInputData()
win.show()
sys.exit(app.exec_())