How to create a custom widget with Qt designer in Python/PyQt5

To create a custom widget with Qt Designer in Python and PyQt, you can use the following steps:

1. Create a new class for your custom widget by subclassing QWidget
2. Define any necessary properties and methods for your widget in the new class
3. Use the "Promote To" feature in Qt Designer to use the custom widget class in a Qt Designer .ui file
4. In the Python code that loads the .ui file, use the QMetaObject.connectSlotsByName() method to connect the custom widget to its signals and slots.

Here's an example of a simple custom widget class:

from PyQt5.QtWidgets import QWidget

class MyCustomWidget(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        # set up the user interface
        self.ui =  ...
    def my_custom_method(self):
        pass

Then you can use the "Promote To" feature in the Qt Designer to use the custom widget class in your .ui file, and in the python code that loads the .ui file, you can connect the custom widget to its signals and slots using the 'QMetaObject.connectSlotsByName()' method.

from PyQt5 import uic, QtWidgets

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        uic.loadUi("mainwindow.ui", self)
        QtCore.QMetaObject.connectSlotsByName(self)

It's worth noting that this is a high-level overview and there are many other details and nuances to consider when creating custom widgets with Qt Designer and PyQt.

I trust this helps you! if you have any query you can ask me.