When executing thread, the first execution fails in try statement - python

from PyQt5.QtWidgets import QMainWindow, QApplication,QLineEdit, QPushButton, QWidget, QAction, QTabWidget,QVBoxLayout
from PyQt5.QtCore import (QCoreApplication, QObject, QRunnable, QThread,
QThreadPool, pyqtSignal)
import sys
import os
from shutil import copy2
import _thread
import time
class AThread(QThread):
def run(self):
count = 0
while count < 5:
time.sleep(1)
print("A Increasing")
count += 1
class Example(QWidget):
def __init__(self):
super().__init__()
self.setAcceptDrops(True)
self.setWindowTitle('Learn')
self.setGeometry(300, 300, 300, 150)
self.layout = QVBoxLayout(self)
# Initialize tab screen
self.tabs = QTabWidget()
self.tab1 = QWidget()
self.tab2 = QWidget()
self.tabs.resize(300,200)
# Add tabs
self.tabs.addTab(self.tab1,"Tab 1")
self.tabs.addTab(self.tab2,"Tab 2")
# Create first tab
self.tab1.layout = QVBoxLayout(self)
self.pushButton1 = QPushButton("PyQt5 button")
self.pushButton1.clicked.connect(self.ON_PRESS)
self.textbox = QLineEdit(self)
self.tab1.layout.addWidget(self.textbox )
self.tab1.layout.addWidget(self.pushButton1)
self.tab1.setLayout(self.tab1.layout)
#Create Textbox inputs
# Add tabs to widget
self.layout.addWidget(self.tabs)
self.setLayout(self.layout)
def using_q_thread(self):
app = Example()
thread = AThread()
thread.start()
sys.exit(app.exec_())
def ON_PRESS(self):
###Here is the Issue
try:
self.using_q_thread()
except:
print ("Error: unable to start thread")
###Drag and Drop files to directory
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
ex.show()
Hoping I am asking this correctly, but whenever using QThread there appears to be a bit of a hiccup. the first attempt to access the threaded function causes the try statement to fail, but then it immediately works. Im just curious if this is part of the functionality or if there is any issue with my code.

Avoid using try-except as you see hidden the error, in my personal case I avoid using it as far as I can for this type of problems.
I do not see it necessary to create another Example within using_q_thread, another problem is that thread is a local variable that will be eliminated, so thread must be a member of the class for its scope to increase.
import sys
import time
from PyQt5.QtCore import QThread
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QTabWidget, QPushButton, QLineEdit
class AThread(QThread):
def run(self):
count = 0
while count < 5:
time.sleep(1)
print("A Increasing")
count += 1
class Example(QWidget):
def __init__(self):
super().__init__()
self.setAcceptDrops(True)
self.setWindowTitle('Learn')
self.setGeometry(300, 300, 300, 150)
self.layout = QVBoxLayout(self)
# Initialize tab screen
self.tabs = QTabWidget()
self.tab1 = QWidget()
self.tab2 = QWidget()
self.tabs.resize(300,200)
# Add tabs
self.tabs.addTab(self.tab1,"Tab 1")
self.tabs.addTab(self.tab2,"Tab 2")
# Create first tab
self.tab1.layout = QVBoxLayout()
self.pushButton1 = QPushButton("PyQt5 button")
self.pushButton1.clicked.connect(self.ON_PRESS)
self.textbox = QLineEdit(self)
self.tab1.layout.addWidget(self.textbox )
self.tab1.layout.addWidget(self.pushButton1)
self.tab1.setLayout(self.tab1.layout)
#Create Textbox inputs
# Add tabs to widget
self.layout.addWidget(self.tabs)
def using_q_thread(self):
self.thread = AThread()
self.thread.start()
def ON_PRESS(self):
self.using_q_thread()
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = Example()
ex.show()
sys.exit(app.exec_())

Related

Enable/Disable QTreeWidget from updating

Is it possible to enable/disable a QTreeWidget from updating?
I want to add rows to my tree and update it manually with a button. Obviously when i add a row to the TreeWidget it will be shown in the table. Is there a way to disable this so i can add like 100 rows and than update it once? If not is there a solution with a TreeView?
import sys
from PyQt5.QtCore import QSize
from PyQt5.QtWidgets import QApplication, QMainWindow, QToolBar, QAction, QTreeWidget, QTreeWidgetItem
class Table(QMainWindow):
def __init__(self):
QMainWindow.__init__(self)
self.resize(800, 600)
self.setMinimumSize(QSize(800, 600))
self.table = QTreeWidget()
self.table.setHeaderLabels(["Description", "Price"])
self.setCentralWidget(self.table)
self.car = QTreeWidgetItem(["Car"])
self.house = QTreeWidgetItem(["House"])
self.table.addTopLevelItem(self.car)
self.table.addTopLevelItem(self.house)
toolbar = QToolBar("Toolbar")
carAction = QAction("Car", self)
carAction.triggered.connect(self.addToCar)
houseAction = QAction("House", self)
houseAction.triggered.connect(self.addToHouse)
updateAction = QAction("Update", self)
updateAction.triggered.connect(self.update)
toolbar.addAction(carAction)
toolbar.addAction(houseAction)
toolbar.addAction(updateAction)
self.addToolBar(toolbar)
def addToCar(self):
child = QTreeWidgetItem(["Audi", str(25000)])
self.car.addChild(child)
def addToHouse(self):
child = QTreeWidgetItem(["Villa", str(500000)])
self.house.addChild(child)
def update(self):
pass
if __name__ == "__main__":
app = QApplication(sys.argv)
win = Table()
win.show()
sys.exit( app.exec_() )
I do not know of a way to "suspend" tree updates, but what about using lists to store the children until one decides to update? See the modified example below (modifications are commented):
import sys
from PyQt5.QtCore import QSize
from PyQt5.QtWidgets import QApplication, QMainWindow, QToolBar, QAction, QTreeWidget, QTreeWidgetItem
class Table(QMainWindow):
def __init__(self):
QMainWindow.__init__(self)
self.resize(800, 600)
self.setMinimumSize(QSize(800, 600))
self.table = QTreeWidget()
self.table.setHeaderLabels(["Description", "Price"])
self.setCentralWidget(self.table)
self.car = QTreeWidgetItem(["Car"])
self.house = QTreeWidgetItem(["House"])
self.table.addTopLevelItem(self.car)
self.table.addTopLevelItem(self.house)
# initialize empty lists which will keep track of generated children
self.car_list, self.house_list = [], []
toolbar = QToolBar("Toolbar")
carAction = QAction("Car", self)
carAction.triggered.connect(self.addToCar)
houseAction = QAction("House", self)
houseAction.triggered.connect(self.addToHouse)
updateAction = QAction("Update", self)
updateAction.triggered.connect(self.update)
toolbar.addAction(carAction)
toolbar.addAction(houseAction)
toolbar.addAction(updateAction)
self.addToolBar(toolbar)
def addToCar(self):
child = QTreeWidgetItem(["Audi", str(25000)])
# instead of adding them directly to the tree, keep them in the list
self.car_list.append(child)
def addToHouse(self):
child = QTreeWidgetItem(["Villa", str(500000)])
# instead of adding them directly to the tree, keep them in the list
self.house.addChild(child)
def update(self):
# update the tree and reset the lists
self.car.addChildren(self.car_list)
self.house.addChildren(self.house_list)
self.car_list, self.house_list = [], []
if __name__ == "__main__":
app = QApplication(sys.argv)
win = Table()
win.show()
sys.exit( app.exec_() )

Implement QThread with QProgressBar in PySide (or PyQt) during calculation

I would like to know how to implement QProgressBar, which shows the progress of calculation in main thread.
Please refer to below codes.
import sys
from PySide2.QtWidgets import QApplication, QWidget, QPushButton, QVBoxLayout, QProgressBar
from PySide2.QtCore import QThread
class BarThread(QThread):
# Progress Bar UI Definition
def __init__(self):
QThread.__init__(self)
self.window = QWidget()
self.pgsb = QProgressBar()
self.lay = QVBoxLayout()
self.lay.addWidget(self.pgsb)
self.window.setLayout(self.lay)
self.isRun = False
# Thread Function Definition
def run(self):
self.window.show()
while self.isRun:
self.pgsb.setValue(self.percent)
print(self.percent)
if self.percent == 100:
self.isRun = False
class Tool(QWidget):
# Main UI Definition
def __init__(self):
windowWidth = 300
windowHeight = 300
QWidget.__init__(self)
self.setWindowTitle("Example")
self.resize(windowWidth, windowHeight)
self.bt = QPushButton('Numbering')
self.layout = QVBoxLayout()
self.layout.addWidget(self.bt)
self.setLayout(self.layout)
# Main Function Link Definition
self.bt.clicked.connect(self.numbering)
# Main Function Definition
def numbering(self):
bth = BarThread()
bth.start()
bth.isRun = True
for x in range(0,100000):
bth.percent = x/1000
print(x)
if __name__ == "__main__":
app = QApplication(sys.argv)
widget = Tool()
widget.show()
sys.exit(app.exec_())
You can copy and paste directly onto your python IDE.
(it needs PySide2. It can be installed with 'pip install pyside2' in your prompt).
This code executes simple numbering, however, this doesn't show numbering progress.
How can I solve this problem? Thank you in advance.
P.S. I'm using Windows 10 with PyCharm.
You have at least the following errors:
You must not modify the GUI from another thread, in your case the run method is executed in another thread but you try to modify the value of the QProgressBar, in addition to displaying a widget which is not allowed. If you want to modify the GUI with the information provided in the execution in the secondary thread you must do it through signals since they are thread-safe
The for loop is the blocking task so it must be executed in another thread.
Considering the above, the solution is:
import sys
from PySide2.QtWidgets import (
QApplication,
QWidget,
QPushButton,
QVBoxLayout,
QProgressBar,
)
from PySide2.QtCore import QThread, Signal
class ProgressWidget(QWidget):
def __init__(self, parent=None):
super(ProgressWidget, self).__init__(parent)
self.pgsb = QProgressBar()
lay = QVBoxLayout(self)
lay.addWidget(self.pgsb)
class BarThread(QThread):
progressChanged = Signal(int)
def run(self):
percent = 0
for x in range(0, 100000):
percent = x / 100
self.progressChanged.emit(percent)
class Tool(QWidget):
"""Main UI Definition"""
def __init__(self, parent=None):
super(Tool, self).__init__(parent)
self.setWindowTitle("Example")
self.resize(300, 300)
self.bt = QPushButton("Numbering")
layout = QVBoxLayout(self)
layout.addWidget(self.bt)
# Main Function Link Definition
self.bt.clicked.connect(self.numbering)
self.bar_thread = BarThread(self)
self.progress_widget = ProgressWidget()
self.bar_thread.progressChanged.connect(self.progress_widget.pgsb.setValue)
# Main Function Definition
def numbering(self):
self.bar_thread.start()
self.progress_widget.show()
def closeEvent(self, event):
super(Tool, self).closeEvent(event)
self.bar_thread.quit()
self.bar_thread.wait()
if __name__ == "__main__":
app = QApplication(sys.argv)
widget = Tool()
widget.show()
sys.exit(app.exec_())

How to show new QMainWindow in every loop in PyQT5?

I'm trying to write a Python program using PyQt5 that will display a window in each iteration of the for loop. I would like to close after incrementing and displaying the next window. However, I do not know how to stop the loop every iteration and at the moment I am getting 6 windows at once.
main.py
import sys
from PyQt5.QtWidgets import (QLineEdit, QVBoxLayout, QMainWindow,
QWidget, QDesktopWidget, QApplication, QPushButton, QLabel,
QComboBox, QFileDialog, QRadioButton)
from PyQt5.QtCore import pyqtSlot, QByteArray
from alert import Window2
from test import test
class SG(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.resize(300, 150)
self.setWindowTitle('TEST')
self.resultsGen = QPushButton('TEST', self)
self.resultsGen.clicked.connect(lambda: self.on_click())
self.show()
#pyqtSlot()
def on_click(self):
test(self)
if __name__ == '__main__':
app = QApplication(sys.argv)
sg = SG()
sys.exit(app.exec_())
alert.py
from PyQt5.QtWidgets import (QLineEdit, QVBoxLayout, QMainWindow,
QWidget, QDesktopWidget, QApplication, QPushButton, QLabel,
QComboBox, QFileDialog, QRadioButton)
from PyQt5.QtCore import pyqtSlot, QByteArray
from PyQt5.QtGui import QPixmap
from PyQt5 import QtGui, QtCore
class Window2(QMainWindow):
def __init__(self):
super().__init__()
self.initPopup()
def initPopup(self):
self.resize(500, 500)
self.setWindowTitle("Window22222")
self.central_widget = QWidget()
self.setCentralWidget(self.central_widget)
lay = QVBoxLayout(self.central_widget)
label = QLabel(self)
pixmap = QPixmap('cropped/8.png')
label.setPixmap(pixmap)
self.resize(pixmap.width(), pixmap.height())
lay.addWidget(label)
self.textbox = QLineEdit(self)
self.textbox.move(20, 20)
self.textbox.resize(280, 40)
# Create a button in the window
self.button = QPushButton('Show text', self)
self.button.move(20, 80)
# connect button to function on_click
self.button.clicked.connect(lambda: self.on_clickX())
self.show()
#pyqtSlot()
def on_clickX(self):
textboxValue = self.textbox.text()
print(textboxValue)
self.textbox.setText("")
self.hide()
test.py
from alert import Window2
def test(self):
for x in range(6):
w = Window2()
As soon as you run the for cycle, all the code of the initialization will be executed, which includes the show() call you used at the end of initPopup().
A simple solution is to create a new signal that is emitted whenever you hide a window, and connect that signal to a function that creates a new one until it reaches the maximum number.
main.py:
import sys
from PyQt5.QtWidgets import QWidget, QApplication, QPushButton
from alert import Window2
class SG(QWidget):
def __init__(self):
super().__init__()
self.initUI()
self.alerts = []
def initUI(self):
self.resize(300, 150)
self.setWindowTitle('TEST')
self.resultsGen = QPushButton('TEST', self)
self.resultsGen.clicked.connect(self.nextAlert)
self.show()
def nextAlert(self):
if len(self.alerts) >= 6:
return
alert = Window2()
self.alerts.append(alert)
alert.setWindowTitle('Window {}'.format(len(self.alerts)))
alert.closed.connect(self.nextAlert)
alert.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
sg = SG()
sys.exit(app.exec_())
alert.py:
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
class Window2(QMainWindow):
closed = pyqtSignal()
def __init__(self):
super().__init__()
self.initPopup()
def initPopup(self):
self.resize(500, 500)
self.central_widget = QWidget()
self.setCentralWidget(self.central_widget)
lay = QVBoxLayout(self.central_widget)
label = QLabel(self)
pixmap = QPixmap('cropped/8.png')
label.setPixmap(pixmap)
self.resize(pixmap.width(), pixmap.height())
lay.addWidget(label)
self.textbox = QLineEdit(self)
lay.addWidget(self.textbox)
# Create a button in the window
self.button = QPushButton('Show text', self)
lay.addWidget(self.button)
# connect button to function on_click
self.button.clicked.connect(lambda: self.on_clickX())
self.show()
#pyqtSlot()
def on_clickX(self):
textboxValue = self.textbox.text()
print(textboxValue)
self.textbox.setText("")
self.hide()
self.closed.emit()
Just note that with this very simplified example the user might click on the button of the "SG" widget even if an "alert" window is visibile. You might prefer to use a QDialog instead of a QMainWindow and make the main widget a parent of that dialog.
main.py:
class SG(QWidget):
# ...
def nextAlert(self):
if len(self.alerts) >= 6:
return
alert = Window2(self)
# ...
alert.py:
class Window2(QDialog):
closed = pyqtSignal()
def __init__(self, parent):
super().__init__()
self.initPopup()
def initPopup(self):
self.resize(500, 500)
# a QDialog doesn't need a central widget
lay = QVBoxLayout(self)
# ...
Also, if an alert window is closed using the "X" button the new one will not be shown automatically. To avoid that, you can implement the "closeEvent" and ignore the event, so that the user will not be able to close the window until the button is clicked. As QDialogs can close themself when pressing the escape key, I'm also ignoring that situation.
alert.py:
class Window2(QMainWindow):
# ...
def closeEvent(self, event):
event.ignore()
def keyPressEvent(self, event):
if event.key() != Qt.Key_Escape:
super().keyPressEvent(event)

PyQt4 using global variable from function in class

I understand that to use a global variable from a function, you Need to execute the function first:
def f():
global s
s = 'Hello'
f()
print(s)
But how do I use variable s globally in following example:
import sys
from PyQt4.QtGui import QApplication, QMainWindow, QPushButton, QLineEdit, QLabel, QComboBox, QProgressBar, QFileDialog
from PyQt4.QtCore import QSize, pyqtSlot
class App(QMainWindow):
def __init__(self):
super(App, self).__init__()
self.setGeometry(500, 300, 820, 350)
self.setWindowTitle("Widget")
self.initUI()
def initUI(self):
#Buttons
btnposx = 30
btnposy = 50
self.btn4 = QPushButton('GetValue', self)
self.btn4.move(btnposx,btnposy+220)
self.btn4.clicked.connect(self.cb_get)
self.cb = QComboBox(self)
self.cb.move(btnposx+120,btnposy+150)
self.cb.resize(80,22)
self.cb.setMaximumSize(QSize(80,1000000))
self.cb.addItem('A')
self.cb.addItem('B')
self.cb.addItem('C')
self.cb.addItem('D')
self.cb.addItem('E')
self.show()
#pyqtSlot()
def cb_get(self):
global s
cbtext = str(self.cb.currentText())
s = cbtext
print(s)
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = App()
sys.exit(app.exec_())
This code shows a PyQt4 Widget. Function cb_get acquires the Value of a QcomboBox and can be used within the class App(). The Value is saved to variable s. How do I use variable s globally?
The only way I seem to get it to work is to write a new function for s and execute it on button click:
import sys
from PyQt4.QtGui import QApplication, QMainWindow, QPushButton, QLineEdit, QLabel, QComboBox, QProgressBar, QFileDialog
from PyQt4.QtCore import QSize, pyqtSlot
class App(QMainWindow):
def __init__(self):
super(App, self).__init__()
self.setGeometry(500, 300, 820, 350)
self.setWindowTitle("Widget")
self.initUI()
def initUI(self):
#Buttons
btnposx = 30
btnposy = 50
self.btn4 = QPushButton('GetValue', self)
self.btn4.move(btnposx,btnposy+220)
self.btn4.clicked.connect(self.cb_get)
self.btn4.clicked.connect(self.p)
self.cb = QComboBox(self)
self.cb.move(btnposx+120,btnposy+150)
self.cb.resize(80,22)
self.cb.setMaximumSize(QSize(80,1000000))
self.cb.addItem('A')
self.cb.addItem('B')
self.cb.addItem('C')
self.cb.addItem('D')
self.cb.addItem('E')
self.show()
#pyqtSlot()
def cb_get(self):
global s
s = str(self.cb.currentText())
def p(self):
print(s)
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = App()
sys.exit(app.exec_())
Well, at least now it has ist own function and I can write code for it seperately.
def initUI(self):
#Buttons
btnposx = 30
btnposy = 50
self.btn4 = QPushButton('GetValue', self)
self.btn4.move(btnposx,btnposy+220)
self.btn4.clicked.connect(self.cb_get)
self.cb = QComboBox(self)
self.cb.move(btnposx+120,btnposy+150)
self.cb.resize(80,22)
self.cb.setMaximumSize(QSize(80,1000000))
self.cb.addItem('A')
self.cb.addItem('B')
self.cb.addItem('C')
self.cb.addItem('D')
self.cb.addItem('E')
self.s = None # initialize it here so you don't have to use global
self.show()
#pyqtSlot()
def cb_get(self):
cbtext = str(self.cb.currentText())
self.s = cbtext
def get_s(self):
return self.s
and
if __name__ == '__main__':
app = QApplication(sys.argv)
ex = App()
# print(ex.get_s) # this won't work since you have to click on btn4 first
sys.exit(app.exec_())

How to detect dialog's close event?

Hi everyone.
I am making a GUI application using python3.4, PyQt5 in windows 7.
Application is very sample. User clicks a main window's button, information dialog pops up. And when a user clicks information dialog's close button (window's X button), system shows confirm message. This is all.
Here's my code.
# coding: utf-8
import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QDialog, QLabel
class mainClass(QMainWindow):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
openDlgBtn = QPushButton("openDlg", self)
openDlgBtn.clicked.connect(self.openChildDialog)
openDlgBtn.move(50, 50)
self.setGeometry(100, 100, 200, 200)
self.show()
def openChildDialog(self):
childDlg = QDialog(self)
childDlgLabel = QLabel("Child dialog", childDlg)
childDlg.resize(100, 100)
childDlg.show()
if __name__ == "__main__":
app = QApplication(sys.argv)
mc = mainClass()
sys.exit(app.exec_())
Result screen shot is...
In this situation, I've added these code in mainClass class.
def closeEvent(self, event):
print("X is clicked")
This code works only when the main window is closed. But what I want is closeEvent function works when childDlg is to closed. Not main window.
What should I do?
You have added, the method closeEvent in the class mainClass.
So you have reimplemented the method closeEvent of your QMainwindow and not the method closeEvent of your childDlg. To do it, you have to subclass your chilDlg like this:
# coding: utf-8
import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QDialog, QLabel
class ChildDlg(QDialog):
def closeEvent(self, event):
print("X is clicked")
class mainClass(QMainWindow):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
openDlgBtn = QPushButton("openDlg", self)
openDlgBtn.clicked.connect(self.openChildDialog)
openDlgBtn.move(50, 50)
self.setGeometry(100, 100, 200, 200)
self.show()
def openChildDialog(self):
childDlg = ChildDlg(self)
childDlgLabel = QLabel("Child dialog", childDlg)
childDlg.resize(100, 100)
childDlg.show()
if __name__ == "__main__":
app = QApplication(sys.argv)
mc = mainClass()
sys.exit(app.exec_())
import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QDialog, QLabel
class mainClass(QMainWindow):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
openDlgBtn = QPushButton("openDlg", self)
openDlgBtn.clicked.connect(self.openChildDialog)
openDlgBtn.move(50, 50)
self.setGeometry(100, 100, 200, 200)
self.show()
def openChildDialog(self):
childDlg = QDialog(self)
childDlgLabel = QLabel("Child dialog", childDlg)
childDlg.closeEvent = self.CloseEvent
childDlg.resize(100, 100)
childDlg.show()
def CloseEvent(self, event):
print("X is clicked")
if __name__ == "__main__":
app = QApplication(sys.argv)
mc = mainClass()
sys.exit(app.exec_())

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