PyQt5 显示窗口后运行函数

Question

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.

Answer 1

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

Answer 2

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()
    ...

Answer 3

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_())  

Answer 4

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.