How to change html elements immediately after loading page with QWebEngineView 'loadFinished'?

I want to use QWebEngineView to do more things when the html page loads, instead of manually sending signals to change the html.I manually used the button to send the signal three times, with the initial load once for a total of four times:

>>

sendCustomSignal to js...
sendCustomSignal to js...
sendCustomSignal to js...
sendCustomSignal to js...

run.py

import os
from time import time
from PyQt5.QtCore import QUrl, pyqtSignal
from PyQt5.QtWebChannel import QWebChannel
from PyQt5.QtWebEngineWidgets import QWebEngineView
from PyQt5.QtWidgets import QWidget, QVBoxLayout, QPushButton


class WebEngineView(QWebEngineView):
    customSignal = pyqtSignal(str)

    def __init__(self, *args, **kwargs):
        super(WebEngineView, self).__init__(*args, **kwargs)
        self.channel = QWebChannel(self)
        self.channel.registerObject('Bridge', self)
        self.page().setWebChannel(self.channel)

    def sendCustomSignal(self):
        print("sendCustomSignal to js...")
        self.customSignal.emit('current time:' + str(time()))


class Window(QWidget):
    def __init__(self, *args, **kwargs):
        super(Window, self).__init__(*args, **kwargs)
        layout = QVBoxLayout(self)
        self.webview = WebEngineView(self)
        layout.addWidget(self.webview)
        layout.addWidget(QPushButton('Send', self, clicked=self.webview.sendCustomSignal))
        self.webview.load(QUrl.fromLocalFile(os.path.abspath('show.html')))
        self.webview.loadFinished.connect(self.webview.sendCustomSignal)


if __name__ == "__main__":
    from PyQt5.QtWidgets import QApplication
    import sys
    app = QApplication(sys.argv)
    w = Window()
    w.show()
    sys.exit(app.exec_())

show.html

<!DOCTYPE html>
<html lang="en">
    <p id="log"></p>
    <script src="qwebchannel.js"></script>
    <script>
            new QWebChannel(qt.webChannelTransport,
                function(channel) {
                    window.Bridge = channel.objects.Bridge;
                    Bridge.customSignal.connect(function(text) {
                       showLog("Signal received：" + text);
                    });
                }
            );
            function showLog(text) {
                var ele = document.getElementById("result");
                ele.value = ele.value + text + "\n";
            }
        </script>
    <h1>Hello PyQt!</h1>
    <textarea id="result" rows="20" cols="100"></textarea>
</html>

Solution

That the signal is emitted emits the loadFinished signal does not imply that all the scripts are executed, in this case it is preferable that the exported object invokes a slot to indicate that the connection has been made.

import os
from time import time
from PyQt5.QtCore import QUrl, pyqtSignal, pyqtSlot
from PyQt5.QtWebChannel import QWebChannel
from PyQt5.QtWebEngineWidgets import QWebEngineView
from PyQt5.QtWidgets import QWidget, QVBoxLayout, QPushButton


class WebEngineView(QWebEngineView):
    customSignal = pyqtSignal(str)

    def __init__(self, *args, **kwargs):
        super(WebEngineView, self).__init__(*args, **kwargs)
        self.channel = QWebChannel(self)
        self.channel.registerObject("Bridge", self)
        self.page().setWebChannel(self.channel)

    def sendCustomSignal(self):
        print("sendCustomSignal to js...")
        self.customSignal.emit("current time:" + str(time()))

    @pyqtSlot()
    def init(self):
        self.sendCustomSignal()


class Window(QWidget):
    def __init__(self, *args, **kwargs):
        super(Window, self).__init__(*args, **kwargs)
        layout = QVBoxLayout(self)
        self.webview = WebEngineView(self)
        layout.addWidget(self.webview)
        layout.addWidget(
            QPushButton("Send", self, clicked=self.webview.sendCustomSignal)
        )
        self.webview.load(QUrl.fromLocalFile(os.path.abspath("show.html")))


if __name__ == "__main__":
    from PyQt5.QtWidgets import QApplication
    import sys

    sys.argv.append("--remote-debugging-port=8000")
    app = QApplication(sys.argv)
    w = Window()
    w.show()
    sys.exit(app.exec_())

<!DOCTYPE html>
<html lang="en">
    <p id="log"></p>
    <script type="text/javascript" src="qrc:///qtwebchannel/qwebchannel.js"></script>
    <script>
        window.onload = function(){
            new QWebChannel(qt.webChannelTransport,
                function(channel) {
                    window.Bridge = channel.objects.Bridge;
                    Bridge.customSignal.connect(function(text) {
                       showLog("Signal received：" + text);
                    });
                    Bridge.init();
                }
            );
            function showLog(text) {
                var ele = document.getElementById("result");
                ele.value = ele.value + text + "\n";
            }
        }
        </script>
    <h1>Hello PyQt!</h1>
    <textarea id="result" rows="20" cols="100"></textarea>
</html>