PyQt - Create QLabels at runtime and change text afterwards

Question

i want to create QLabels dynamically at runtime, and change the Text afterwards. I did it like that:

def __init__(self, *args, **kwargs):
    QWidget.__init__(self, *args, **kwargs)
    self.counter = 0
    self.items = self.read_hosts()
    self.layout = QGridLayout()
    for item in self.items:
        self.item = QLabel(item, self)

        self.item.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
        self.item.setAlignment(Qt.AlignCenter)
        self.item.setStyleSheet("QLabel {background-color: green;}")
        self.layout.addWidget(self.item,self.counter, 0)
        self.counter += 1
    self.setLayout(self.layout)
    self.startWorker()
    self.show()

def change_txt(self, lb, i):
     self.item.setText("{}".format(i))

It won't work. I understand why it would change just the text of the last label. I'm doing something wrong during assignment.

How can I create all labels completely variably and subsequently change the texts?

I am using:

PyQT5 on Windows 10

Thanks!

Here is my whole code:

import sys
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import os

class Worker(QObject):
    update = pyqtSignal(str,int)
    exception = pyqtSignal(str)

    def read_hosts(self):
        #try:
            file = open("hosts.ini", "r") 
            return file.readlines() 
        #except Exception as ex:
            #self.exception.emit(str(ex))

    def check_ping(self):
        #try:
            hosts = self.read_hosts()
            while True:
                for host in hosts:
                    print(host)
                    params = " -l 1000"
                    response = os.system("ping  " + host + params)
                    print("weiter")
                    self.update.emit(host, response)

        #except Exception as ex:
            #self.exception.emit(str(ex))

class Window(QWidget):
    def __init__(self, *args, **kwargs):
        QWidget.__init__(self, *args, **kwargs)

        self.counter = 0
        self.items = self.read_hosts()
        self.layout = QGridLayout()
        for item in self.items:
            self.item = QLabel(item, self)
            self.item.setObjectName("label" + str(self.counter))
            print("label" + str(self.counter))
            self.item.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
            self.item.setAlignment(Qt.AlignCenter)
            self.item.setStyleSheet("QLabel {background-color: green;}")
            self.layout.addWidget(self.item,self.counter, 0)
            self.counter += 1
        self.setLayout(self.layout)
        self.startWorker()
        self.show()

    def startWorker(self):
        self.thread = QThread() 
        self.obj = Worker()  
        self.thread = QThread() 
        self.obj.moveToThread(self.thread)
        self.obj.update.connect(self.onUpdate)
        self.obj.exception.connect(self.onException)
        self.thread.started.connect(self.obj.check_ping)
        self.thread.start()

    def read_hosts(self):
        #try:
            file = open("hosts.ini", "r") 
            return file.readlines() 
        #except Exception as ex:
            #self.exception.emit(str(ex))

    def onException(self, msg):
        QMessageBox.warning(self, "Eine Exception im Worker wurde geworfen: ", msg)

    def onUpdate(self, lb, i):
        label = lb
        self.label0.setText("{}".format(i))


app = QApplication(sys.argv)
win = Window()
sys.exit(app.exec_())

hosts.ini:

192.168.1.1
192.168.1.2
192.168.1.30

Could you explain yourself better, do you want to change all the QLabels at the same time or before what action do you want to change each QLabel? — eyllanesc
First I want to create a label assigning an ObjectName from a list and then I want to change the text of the label afterwards. After creation of labels a thread will emit an signal and this method should change the right one label(text). — 0xPYTHONIC

eyllanesc eyllanesc · Accepted Answer · 2018-05-27T19:09:39

I have improved your code in the following aspects:

If your layout has a column it is not necessary to use QGridLayout, just QVBoxLayout.
Having a read_hosts() method for each class is a waste, so I've created a unique function.
self.item is an attribute of the class that is continually being overwritten so it is not necessary to create them.
The objectName should be the name of the host, that is, the IP, since that is the information that the thread has.
To find the label through the objectName you can use findChild().

import sys
import os

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

def read_hosts():
    file = open("hosts.ini", "r") 
    return file.readlines() 

class Worker(QObject):
    update = pyqtSignal(str, int)
    exception = pyqtSignal(str)

    def check_ping(self):
        hosts = read_hosts()
        while True:
            for host in hosts:
                params = "-l 1000"
                response = os.system("ping  {} {}".format(host, params))
                print("weiter")
                self.update.emit(host, response)

class Window(QWidget):
    def __init__(self, *args, **kwargs):
        QWidget.__init__(self, *args, **kwargs)
        self.layout = QVBoxLayout(self)

        hosts = read_hosts()
        for host in hosts:
            label = QLabel(host)
            label.setObjectName(host)
            label.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
            label.setAlignment(Qt.AlignCenter)
            label.setStyleSheet("QLabel {background-color: green;}")
            self.layout.addWidget(label)
        self.startWorker()

    def startWorker(self):
        self.thread = QThread() 
        self.obj = Worker()  
        self.thread = QThread() 
        self.obj.moveToThread(self.thread)
        self.obj.update.connect(self.onUpdate)
        self.obj.exception.connect(self.onException)
        self.thread.started.connect(self.obj.check_ping)
        self.thread.start()

    def onException(self, msg):
        QMessageBox.warning(self, "Eine Exception im Worker wurde geworfen: ", msg)

    def onUpdate(self, host, value):
        label = self.findChild(QLabel, host)
        label.setText("{}".format(value))

if __name__ == '__main__':
    app = QApplication(sys.argv)
    win = Window()
    win.show()
    sys.exit(app.exec_())

PyQt - Create QLabels at runtime and change text afterwards

1 Answers