Once you have created a graphical user interface (GUI) of your application using PyQt5Designer tool, then the next step is to create a Python file and use this .ui file. Launch PyCharm from Start menu and open the FirstGUIApp project, which was created in the earlier post. I already saved the 'appGUI.ui' file in the same project directory.
Right-click on the project, click New from the menu and then select Python File, as shown in the figure below:
Enter the new filename e.g. 'FirstApp and click on OK button.
It creates an empty python file, it opens this file as shown below:
Python has the major advantage of having a short-code and this is one of the greatest features of python language. There are few ways to work with loading .ui file into python file. We will create a class first namely FirstApp (you can name it whatever you like). In python, 'def' keyword is used to define a method, following the name of the method. Similarly, '_ _init_ _' is a reserved method and used as a constructor of the class, in python. To access the methods and instances of the class in python, 'self' keyword is used. It represents the instance of that class.
In the class constructor, we set the Title, Width, and Height of the GUI window. It will set the title of the window with a fixed width and height as defined. The width and height of the window will be the same as defined in the 'appGUI.ui' file. We can confirm these in PyQt5Designer tool as shown below:
We need a QApplication object before QWidget. After this, we load the 'appGUI.ui' file in another method. This is all we should have in the class constructor.
For instance, no need to know about the imports, we can talk about these later.
Then we define another method namely 'init_ui' to initialize the UI and its components. First, we load our 'appGUI.ui' file and assign it to 'self.ui_window' object. Then we set the title, width, and height using 'self.title', 'self.width', and 'self.height' respectively, which we already defined in the class constructor. Finally, we need to show this window using 'self.ui_window.show()'. That's all about the initialization of the graphical user interface in the python file.
Now, we need to run the python file to display our application GUI. In the python, we can build and run a single python file separately instead of the complete project. If we run this python file, then nothing will be displayed since we only defined the class constructor with 'init_ui' method but didn't call these. For this, we need to call the class constructor by class name following by empty parenthesis ().
Let's run this python file, and it will load and display our 'appGUI.ui' file as shown below:
We can enter the text in the given input box, and click on the Click Me button. Nothing will happen since we didn't handle the Click Event for this button. Next, we define a method 'show_text' and write just a single statement to print whatever is entered in the input box, on the graphical user interface. Then call this method, on the button click.
'print_text' is the method which contains a single statement. 'textLineEdit' is the objectName of QLineEdit (i.e. input box), and its text will be printed on the console. The statement next to the arrow shown in the figure above is the click event. 'clickButton' is the push button objectName, and we passed 'self.print_text' method in the 'connect' of Click Me button. When we press this button, it prints the text that is entered in the input box, to the console. Let's run the python file and see how it works.
In the above figure, text ' Hi, welcome to GUI application.' is entered in the input box. When we click on Click Me button, then it prints this text on the Console as shown on the bottom-left block.
That's all, how to create a Python file, load GUI and interact with GUI of the application.
Right-click on the project, click New from the menu and then select Python File, as shown in the figure below:
Enter the new filename e.g. 'FirstApp and click on OK button.
It creates an empty python file, it opens this file as shown below:
Python has the major advantage of having a short-code and this is one of the greatest features of python language. There are few ways to work with loading .ui file into python file. We will create a class first namely FirstApp (you can name it whatever you like). In python, 'def' keyword is used to define a method, following the name of the method. Similarly, '_ _init_ _' is a reserved method and used as a constructor of the class, in python. To access the methods and instances of the class in python, 'self' keyword is used. It represents the instance of that class.
In the class constructor, we set the Title, Width, and Height of the GUI window. It will set the title of the window with a fixed width and height as defined. The width and height of the window will be the same as defined in the 'appGUI.ui' file. We can confirm these in PyQt5Designer tool as shown below:
We need a QApplication object before QWidget. After this, we load the 'appGUI.ui' file in another method. This is all we should have in the class constructor.
For instance, no need to know about the imports, we can talk about these later.
Then we define another method namely 'init_ui' to initialize the UI and its components. First, we load our 'appGUI.ui' file and assign it to 'self.ui_window' object. Then we set the title, width, and height using 'self.title', 'self.width', and 'self.height' respectively, which we already defined in the class constructor. Finally, we need to show this window using 'self.ui_window.show()'. That's all about the initialization of the graphical user interface in the python file.
Now, we need to run the python file to display our application GUI. In the python, we can build and run a single python file separately instead of the complete project. If we run this python file, then nothing will be displayed since we only defined the class constructor with 'init_ui' method but didn't call these. For this, we need to call the class constructor by class name following by empty parenthesis ().
Let's run this python file, and it will load and display our 'appGUI.ui' file as shown below:
We can enter the text in the given input box, and click on the Click Me button. Nothing will happen since we didn't handle the Click Event for this button. Next, we define a method 'show_text' and write just a single statement to print whatever is entered in the input box, on the graphical user interface. Then call this method, on the button click.
'print_text' is the method which contains a single statement. 'textLineEdit' is the objectName of QLineEdit (i.e. input box), and its text will be printed on the console. The statement next to the arrow shown in the figure above is the click event. 'clickButton' is the push button objectName, and we passed 'self.print_text' method in the 'connect' of Click Me button. When we press this button, it prints the text that is entered in the input box, to the console. Let's run the python file and see how it works.
In the above figure, text ' Hi, welcome to GUI application.' is entered in the input box. When we click on Click Me button, then it prints this text on the Console as shown on the bottom-left block.
That's all, how to create a Python file, load GUI and interact with GUI of the application.
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