Note that the scroll functionality has not been triggered, and no scrollbar has appeared on the right hand side. Instead the labels are still progressively getting smaller in height to accommodate the widgets.

However, if we set Vertical Policy to Fixed and set the minimumSize of height to 100px the labels will no longer be able to shrink vertically into the available space. As the layout overflows this will now trigger the QScrollArea to display a scrollbar.

With that, our scrollbar appears on the right hand side. What has happened is that the scroll area only appears when necessary. Without a fixed height constraint on the widget, Qt assumes the most logical way to handle the many widgets is to resize them. But by imposing size constraints on our widgets, the scroll bar appears to allow all widgets to keep their fixed sizes.

Another important thing to note is the properties of the scroll area. Instead of adjusting fixed heights, we can keep it in Preferred , we can set the properties of the verticalScrollBar to ScrollBarAlwaysOn which will enable the scroll bar to appear sooner as below

Saving and running the code at the start of this tutorial gives us this scroll area app which is what we wanted.

Adding a QScrollArea from code

As with all widgets you can also add a QScrollArea directly from code. Below we repeat the above example, with a flexible scroll area for a given number of widgets, using code.

from PyQt5.QtWidgets import (QWidget, QSlider, QLineEdit, QLabel, QPushButton, QScrollArea,QApplication,
                             QHBoxLayout, QVBoxLayout, QMainWindow)
from PyQt5.QtCore import Qt, QSize
from PyQt5 import QtWidgets, uic
import sys
class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.initUI()
    def initUI(self):
        self.scroll = QScrollArea()             # Scroll Area which contains the widgets, set as the centralWidget
        self.widget = QWidget()                 # Widget that contains the collection of Vertical Box
        self.vbox = QVBoxLayout()               # The Vertical Box that contains the Horizontal Boxes of  labels and buttons
        for i in range(1,50):
            object = QLabel("TextLabel")
            self.vbox.addWidget(object)
        self.widget.setLayout(self.vbox)
        #Scroll Area Properties
        self.scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
        self.scroll.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.scroll.setWidgetResizable(True)
        self.scroll.setWidget(self.widget)
        self.setCentralWidget(self.scroll)
        self.setGeometry(600, 100, 1000, 900)
        self.setWindowTitle('Scroll Area Demonstration')
        self.show()
        return
def main():
    app = QtWidgets.QApplication(sys.argv)
    main = MainWindow()
    sys.exit(app.exec_())
if __name__ == '__main__':
    main()
If you run the above code you should see the output below, with a custom widget repeated multiple times down the window, and navigable using the scrollbar on the right.
Scroll Area App

Next, we'll step through the code to explain how this view is constructed.
First we create our layout hierarchy. At the top level we have our QMainWindow which we can set the QScrollArea onto using .setCentralWidget. This places the QScrollArea in the window, taking up the entire area.
To add content to the QScrollArea we need to add a widget using .setWidget, in this case we are adding a custom QWidget onto which we have applied a QVBoxLayout containing multiple sub-widgets.
python
def initUI(self):
        self.scroll = QScrollArea()             # Scroll Area which contains the widgets, set as the centralWidget
        self.widget = QWidget()                 # Widget that contains the collection of Vertical Box
        self.vbox = QVBoxLayout()               # The Vertical Box that contains the Horizontal Boxes of  labels and buttons
        for i in range(1,50):
            object = QLabel("TextLabel")
            self.vbox.addWidget(object)
This gives us the following hierarchy in the window:
Finally we set up properties on the QScrollArea, setting the vertical scrollbar Always On and the horizontal Always Off. We allow the widget to be resized, and then add the central placeholder widget to complete the layout.
python
#Scroll Area Properties
self.scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
self.scroll.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
self.scroll.setWidgetResizable(True)
self.scroll.setWidget(self.widget)
Finally, we will add the QScrollArea as the central widget for our QMainWindow and set up the window dimensions, title and show the window.
python
self.setCentralWidget(self.scroll)
self.setGeometry(600, 100, 1000, 900)
self.setWindowTitle('Scroll Area Demonstration')
self.show()
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Conclusion.
In this tutorial we've learned how to add a scrollbar with an unlimited number of widgets, programmatically or using Qt Designer. Adding a QScrollArea is a good way to include multiple widgets especially on apps that are data intensive and require objects to be displayed as lists.
Have a go at making your own apps with QScrollArea and share with us what you have made!
  For more information about using QScrollArea check out the PyQt5 documentation.