How to create a loading warning for long processing thread on python?

Question

I'm fairly new to python(only couple weeks learning) and I'm finishing my first application using python 3.6 and Pyqt5 for GUI. It consists in a blockchain wallet for my boss' company's private blockchain. I have everything working right(miracle if You ask me). I'm using threads so the GUI doesn't get frozen when the blockchain's API takes long to process. So I have this piece of code

def modalCreateAddress():
    name, ok = QInputDialog.getText(None, 'Name the address', 'Enter the address name:')
    if ok:
        _thread.start_new_thread(createAddress, (password, name))

This function createAddress as it seems, pretty obviously, calls the API for a new address creation, it sometimes takes a couple seconds but as it is on a thread the user is free to keep using the GUI and the function just looks like its not working. I wonder how I can manage to have a sort of loading indicator like "Generating new address..." or something like that. What's the best way to approach this situation? Maybe a little progress bar, or loading gif overlay? Would I have to get some sort of callback from the thread so I know when to hide the loading warning? If so, how can I do it?

Not really, a simple pulsing full progreebar or a loading warning would be enough thou... — Marciel Fonseca, Apr 06 '18 at 02:46

eyllanesc · Accepted Answer · 2018-04-06T03:57:09.727

For this type of tasks you can use a QProgressDialog, in the following part there is an example:

import sys
import time
import thread

from PyQt5.QtCore import QObject, pyqtSignal, Qt
from PyQt5.QtWidgets import QWidget, QVBoxLayout, QPushButton, QInputDialog, QApplication, QProgressDialog

class Message(QObject):
    finished = pyqtSignal()

def createAddress(password, name, obj):
    time.sleep(5)
    obj.finished.emit()


class Widget(QWidget):
    def __init__(self, *args, **kwargs):
        QWidget.__init__(self, *args, **kwargs)
        lay = QVBoxLayout(self)
        button = QPushButton("Start processing")
        lay.addWidget(button)
        button.clicked.connect(self.start_task)
        self.message_obj = Message()

    def start_task(self):
        password = "password"
        name, ok = QInputDialog.getText(None, 'Name the address', 'Enter the address name:')
        if ok:
            self.progress_indicator = QProgressDialog(self)
            self.progress_indicator.setWindowModality(Qt.WindowModal)
            self.progress_indicator.setRange(0, 0)
            self.progress_indicator.setAttribute(Qt.WA_DeleteOnClose)
            self.message_obj.finished.connect(self.progress_indicator.close, Qt.QueuedConnection)
            self.progress_indicator.show()
            thread.start_new_thread(createAddress, (password, name, self.message_obj))


if __name__ == '__main__':
    app = QApplication(sys.argv)
    app.setStyle("fusion")
    w = Widget()
    w.show()
    sys.exit(app.exec_())

How to create a loading warning for long processing thread on python?

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