Build a Contact Book With Python, PyQt, and SQLite

Structuring the Contact Book Project

To start coding the application, go ahead and create a new directory called rpcontacts_project/. This will be the project’s root directory. Now create a new subdirectory called rpcontacts/ inside rpcontacts_project/. This subdirectory will hold the application’s main package. Finally, fire up your code editor or IDE within the root directory.

To turn a directory into a package, Python needs an __init__.py module to initialize the package. Create this file within rpcontacts/ and add the following code to it:

# -*- coding: utf-8 -*-

"""This module provides the rpcontacts package."""

__version__ = "0.1.0"

This file tells Python that rpcontacts is a package. The code in the file runs when you import the package or some of its modules.

You don’t need to put any code in an __init__.py file to initialize the package. An empty __init__.py file will do the job. However, in this case, you define a module-level constant called __version__ to hold the version number of your application.

Creating the Application’s Main Window

Now it’s time to create your contact book’s main window. To do that, create a module called views.py in your rpcontacts package. Then add the following code to the module and save it:

# -*- coding: utf-8 -*-

"""This module provides views to manage the contacts table."""

from PyQt5.QtWidgets import (
    QHBoxLayout,
    QMainWindow,
    QWidget,
)

class Window(QMainWindow):
    """Main Window."""
    def __init__(self, parent=None):
        """Initializer."""
        super().__init__(parent)
        self.setWindowTitle("RP Contacts")
        self.resize(550, 250)
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.layout = QHBoxLayout()
        self.centralWidget.setLayout(self.layout)

First, you import the required classes from PyQt5.QtWidgets. Then you create Window. This class inherits from QMainWindow and provides the code to generate the application’s main window. In the initializer method, you set the window’s title to "RP Contacts", resize the window to 550 by 250 pixels, define and set the central widget using QWidget, and finally define a layout for the central widget using a horizontal box layout.

Coding and Running the Application

Since you already have a main window for the contact book, it’s time to write the code for creating a functional PyQt application using QApplication. To do that, create a new module called main.py in your rpcontacts package and add the following code to it:

# -*- coding: utf-8 -*-
# rpcontacts/main.py

"""This module provides RP Contacts application."""

import sys

from PyQt5.QtWidgets import QApplication

from .views import Window

def main():
    """RP Contacts main function."""
    # Create the application
    app = QApplication(sys.argv)
    # Create the main window
    win = Window()
    win.show()
    # Run the event loop
    sys.exit(app.exec())

In this module, you import sys to get access to exit(), which allows you to cleanly exit the application when the user closes the main window. Then you import QApplication from PyQt5.QtWidgets and Window from views. The final step is to define main() as your application’s main function.

Inside main(), you instantiate QApplication and Window. Then you call .show() on Window, and finally you run the application’s main loop, or event loop, using .exec().

Now move up to the project root directory rpcontacts_project/ and create a file called rpcontacts.py. This file provides the entry-point script to run the application. Add the following code to the file and save it:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# rpcontacts_project/rpcontacts.py

"""This module provides RP Contacts entry point script."""

from rpcontacts.main import main

if __name__ == "__main__":
    main()

This file imports main() from your main.py module. Then you implement the traditional conditional statement that calls main() if the user runs this module as a Python script. Now launch the application by running the command python rpcontacts.py in your Python environment. You’ll get the following window on your screen:

That’s it! You’ve created a minimal but functional PyQt GUI application that you can use as a starting point for building your contact book. At this point, your project should have the following structure:

./rpcontacts_project/
│
├── rpcontacts/
│   ├── __init__.py
│   ├── views.py
│   └── main.py
│
└── rpcontacts.py

In this section, you’ve created the minimal required structure for your contact book project using Python modules and packages. You’ve built the application’s main window and put together the boilerplate code to create a PyQt GUI application. You’ve also run the application for the first time. Next, you’ll start adding features to your GUI.

Connecting to the Database With PyQt and SQLite

Connecting your contact book application to its associated database is a fundamental step in developing the application. To do this, you’ll code a function called createConnection(), which will create and open a connection to the database. If the connection is successful, then the function will return True. Otherwise, it will provide information about the cause of the connection failure.

Get back to the rpcontacts/ directory and create a new module called database.py within it. Then add the following code to that module:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/database.py
 3
 4"""This module provides a database connection."""
 5
 6from PyQt5.QtWidgets import QMessageBox
 7from PyQt5.QtSql import QSqlDatabase
 8
 9def createConnection(databaseName):
10    """Create and open a database connection."""
11    connection = QSqlDatabase.addDatabase("QSQLITE")
12    connection.setDatabaseName(databaseName)
13
14    if not connection.open():
15        QMessageBox.warning(
16            None,
17            "RP Contact",
18            f"Database Error: {connection.lastError().text()}",
19        )
20        return False
21
22    return True

Here, you first import some required PyQt classes. Then you define createConnection(). This function takes one argument: databaseName holds the name or path to the physical SQLite database file in your file system.

Here’s what the code inside createConnection() does:

• Line 11 creates the database connection using the QSQLITE driver.
• Line 12 sets the filename or the path to the database.
• Line 14 attempts to open the connection. If a problem occurs during the call to .open(), then the if code block shows an error message and then returns False to indicate that the connection attempt failed.
• Line 22 returns True if the connection attempt is successful.

You already coded createConnection(). Now you can write the code to create the contacts tables in the database.

Creating the contacts Table

With the function that creates and opens the connection to the database in place, you can proceed to code a helper function to create the contacts table. You’ll use this table to store the information about your contacts.

Here’s the code that implements _createContactsTable():

# -*- coding: utf-8 -*-
# rpcontacts/database.py

# Snip...
from PyQt5.QtSql import QSqlDatabase, QSqlQuery

def _createContactsTable():
    """Create the contacts table in the database."""
    createTableQuery = QSqlQuery()
    return createTableQuery.exec(
        """
        CREATE TABLE IF NOT EXISTS contacts (
            id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
            name VARCHAR(40) NOT NULL,
            job VARCHAR(50),
            email VARCHAR(40) NOT NULL
        )
        """
    )

def createConnection(databaseName):
    # Snip...
    _createContactsTable()
    return True

Here, you first add a new import. You import QSqlQuery to execute and manipulate SQL statements.

Inside _createContactsTable(), you create a QSqlQuery instance. Then you call .exec() on the query object with a string-based SQL CREATE TABLE statement as an argument. This statement creates a new table called contacts in your database. The table has the following columns:

The contacts table in your database will store relevant information about your contacts.

The final step to finish coding database.py is to add a call to _createContactsTable() from inside createConnection(), right before the last return statement. This ensures that the application creates the contacts table before doing any operations on the database.

Once you’ve created the contacts table, you can run some tests on the database and also add some sample data for further testing.

Testing the Contact Book’s Database

So far, you’ve finished writing the required code to handle the connection to the contact book’s database. In this section, you’ll perform some tests to make sure that this code and the database itself work properly. You’ll also add some sample data to the database to perform further testing later in this tutorial.

Now open a terminal or command line and move to the project’s root directory, rpcontacts_project/. Once there, launch a Python interactive session and type in the following code:

>>> from rpcontacts.database import createConnection

>>> # Create a connection
>>> createConnection("contacts.sqlite")
True

>>> # Confirm that contacts table exists
>>> from PyQt5.QtSql import QSqlDatabase
>>> db = QSqlDatabase.database()
>>> db.tables()
['contacts', 'sqlite_sequence']

Here, you first import createConnection() from the database.py module. Then you call this function to create and open a connection to the contact database. The database filename is contacts.sqlite. Since this file doesn’t exist in the project’s root directory, SQLite creates it for you. You can check this by taking a look at your current directory.

Next, you confirm that the database contains a table called contacts. To do that, you call .database() on QSqlDatabase. This class method returns a pointer to the current database connection. With this reference to the connection, you can call .tables() to get the list of tables in the database. Note that the first table in the list is contacts, so now you’re sure that everything is working well.

Now you can prepare an SQL query to insert sample data into the contacts table:

>>> # Prepare a query to insert sample data
>>> from PyQt5.QtSql import QSqlQuery

>>> insertDataQuery = QSqlQuery()
>>> insertDataQuery.prepare(
...     """
...     INSERT INTO contacts (
...         name,
...         job,
...         email
...     )
...     VALUES (?, ?, ?)
...     """
... )
True

The above query allows you to insert specific values into the name, job, and email attributes and to save those values to the database. Below is an example of how to do this:

>>> # Sample data
>>> data = [
...     ("Linda", "Technical Lead", "linda@example.com"),
...     ("Joe", "Senior Web Developer", "joe@example.com"),
...     ("Lara", "Project Manager", "lara@example.com"),
...     ("David", "Data Analyst", "david@example.com"),
...     ("Jane", "Senior Python Developer", "jane@example.com"),
... ]

>>> # Insert sample data
>>> for name, job, email in data:
...     insertDataQuery.addBindValue(name)
...     insertDataQuery.addBindValue(job)
...     insertDataQuery.addBindValue(email)
...     insertDataQuery.exec()
...
True
True
True
True
True

In this piece of code, you first define data to hold the contact information of a list of people. Next, you use a for loop to insert the data by calling .addBindValue(). Then you call .exec() on the query object to effectively run the SQL query on the database.

Since all the calls to .exec() return True, you can conclude that the data was successfully inserted into the database. If you want to confirm this, then run the following code:

>>> query = QSqlQuery()
>>> query.exec("SELECT name, job, email FROM contacts")
True

>>> while query.next():
...     print(query.value(0), query.value(1), query.value(2))
...
Linda Technical Lead linda@example.com
Joe Senior Web Developer joe@example.com
Lara Project Manager lara@example.com
David Data Analyst david@example.com
Jane Senior Python Developer jane@example.com

That’s it! Your database works fine! Now you have some sample data to test the application with, and you can focus on how to load and display the contact information in your contact book’s main window.

Creating a Model to Handle the Contact Data

PyQt provides a rich set of classes for working with SQL databases. For your contact book application, you’ll use QSqlTableModel, which provides an editable data model for a single database table. It’s perfect for the job since your database has a single table, contacts.

Get back to your code editor and create a new module called model.py inside the rpcontacts/ directory. Add the following code to the file and save it:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/model.py
 3
 4"""This module provides a model to manage the contacts table."""
 5
 6from PyQt5.QtCore import Qt
 7from PyQt5.QtSql import QSqlTableModel
 8
 9class ContactsModel:
10    def __init__(self):
11        self.model = self._createModel()
12
13    @staticmethod
14    def _createModel():
15        """Create and set up the model."""
16        tableModel = QSqlTableModel()
17        tableModel.setTable("contacts")
18        tableModel.setEditStrategy(QSqlTableModel.OnFieldChange)
19        tableModel.select()
20        headers = ("ID", "Name", "Job", "Email")
21        for columnIndex, header in enumerate(headers):
22            tableModel.setHeaderData(columnIndex, Qt.Horizontal, header)
23        return tableModel

In this code, you first do some required imports, then you create ContactsModel. In the class initializer, you define an instance attribute called .model to hold the data model.

Next, you add a static method to create and set up the model object. Here’s what the code in ._createModel() does:

• Line 16 creates an instance of QSqlTableModel() called tableModel.
• Line 17 associates the model object with the contacts table in your database.
• Line 18 sets the .editStrategy property of the model to QSqlTableModel.OnFieldChange. With this, you ensure that the changes on the model get saved into the database immediately.
• Line 19 loads the table into the model by calling .select().
• Lines 20 to 22 define and set user-friendly headers for the contacts table’s columns.
• Line 23 returns the newly created model.

At this point, you have your data model ready to use. Now you need to connect the table view widget to the model so you can present your users with the contact information.

Connecting the Model to the View

To display contact data in your contact book’s main window, you need to connect the table view with the data model. To perform this connection, you need to call .setModel() on the table view object and pass the model as an argument:

# -*- coding: utf-8 -*-
# rpcontacts/views.py

# Snip...
from .model import ContactsModel

class Window(QMainWindow):
    """Main Window."""
    def __init__(self, parent=None):
        # Snip...
        self.contactsModel = ContactsModel()
        self.setupUI()

    def setupUI(self):
        """Setup the main window's GUI."""
        # Create the table view widget
        self.table = QTableView()
        self.table.setModel(self.contactsModel.model)
        self.table.setSelectionBehavior(QAbstractItemView.SelectRows)
        # Snip...

In this code, you first import ContactsModel from model.py. This class provides the model that manages the data in your contact database.

In the initializer of Window, you create an instance of ContactsModel. Then inside .setupUI(), you call .setModel() on .table to connect the model with the table view. If you run the application after this update, then you’ll get the window you saw at the beginning of step 4.

Displaying and Updating Contacts

PyQt’s Model-View architecture provides a robust and user-friendly way to create GUI applications that manage databases. Models communicate with and access the data in the database. Any change in a model updates the database immediately. Views are responsible for displaying the data to the user and also for providing editable widgets to allow the user to modify the data directly in the view.

If the user modifies the data through the view, then the view internally communicates with and updates the model, which saves the changes to the physical database:

In this example, you double-click Joe’s Job field. This gives you access to an editable widget that allows you to modify the value in the cell. Then you update the job description from Senior Web Developer to Web Developer. When you hit Enter, the table view communicates the change to the model, and the model saves the change to the database immediately.

To confirm that the changes were successfully saved into the database, you can close the application and run it again. The table view should reflect your updates.

Creating the Add Contact Dialog

Dialogs are small windows that you can use to communicate with your users. In this section, you’ll code the contact book’s Add Contact dialog to allow your users add new contacts to their current list of contacts.

To code the Add Contact dialog, you’ll subclass QDialog. This class provides a blueprint to build dialogs for your GUI applications.

Now open the views.py module and update the import section like this:

# -*- coding: utf-8 -*-
# rpcontacts/views.py

# Snip...
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import (
    QAbstractItemView,
    QDialog,
    QDialogButtonBox,
    QFormLayout,
    QHBoxLayout,
    QLineEdit,
    QMainWindow,
    QMessageBox,
    QPushButton,
    QTableView,
    QVBoxLayout,
    QWidget,
)

The highlighted lines in the above code import the required classes to build the Add Contact dialog. With these classes in your namespace, add the following class at the end of views.py:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/views.py
 3
 4# Snip...
 5class AddDialog(QDialog):
 6    """Add Contact dialog."""
 7    def __init__(self, parent=None):
 8        """Initializer."""
 9        super().__init__(parent=parent)
10        self.setWindowTitle("Add Contact")
11        self.layout = QVBoxLayout()
12        self.setLayout(self.layout)
13        self.data = None
14
15        self.setupUI()
16
17    def setupUI(self):
18        """Setup the Add Contact dialog's GUI."""
19        # Create line edits for data fields
20        self.nameField = QLineEdit()
21        self.nameField.setObjectName("Name")
22        self.jobField = QLineEdit()
23        self.jobField.setObjectName("Job")
24        self.emailField = QLineEdit()
25        self.emailField.setObjectName("Email")
26        # Lay out the data fields
27        layout = QFormLayout()
28        layout.addRow("Name:", self.nameField)
29        layout.addRow("Job:", self.jobField)
30        layout.addRow("Email:", self.emailField)
31        self.layout.addLayout(layout)
32        # Add standard buttons to the dialog and connect them
33        self.buttonsBox = QDialogButtonBox(self)
34        self.buttonsBox.setOrientation(Qt.Horizontal)
35        self.buttonsBox.setStandardButtons(
36            QDialogButtonBox.Ok | QDialogButtonBox.Cancel
37        )
38        self.buttonsBox.accepted.connect(self.accept)
39        self.buttonsBox.rejected.connect(self.reject)
40        self.layout.addWidget(self.buttonsBox)

There are a lot of things happening in this code. Here’s a summary:

• Line 5 defines a new class that inherits from QDialog.
• Lines 7 to 15 define the class initializer. In this case, the most relevant addition is .data, which is an instance attribute that you’ll use to hold the data your users provide.

In .setupUI(), you define the dialog’s GUI:

• Lines 20 to 25 add three QLineEdit objects: name, job, and email. You’ll use these line edits to take the user’s input for the name, job description, and email of the contact to add. They represent the corresponding fields in the database.
• Lines 27 to 30 create a QFormLayout instance that arranges the line edits in a form. This layout manager also provides user-friendly labels for each line edit or field.
• Lines 33 to 37 add a QDialogButtonBox object that provides two standard buttons: OK and Cancel. The OK button accepts the user’s input and the Cancel button rejects it.
• Lines 38 and 39 connect the dialog’s built-in .accepted() and .rejected() signals with the .accept() and reject() slots, respectively. In this case, you’ll rely on the dialog’s built-in .reject() slot, which closes the dialog without processing the input. Other than that, you just need to code the .accept() slot.

To code the dialog’s .accept() slot, you need to consider that any user input needs validation to make sure that it’s correct and safe. This is especially true when you’re working with SQL databases because of the risk of an SQL injection attack.

In this example, you’ll add a minimal validation rule just to make sure that the user provides data for each input field in the dialog. However, adding your own, more robust validation rules would be a good exercise.

Without further ado, get back to AddDialog and add the following code for its .accept() slot:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/views.py
 3
 4# Snip...
 5class AddDialog(QDialog):
 6    def __init__(self, parent=None):
 7        # Snip...
 8
 9    def setupUI(self):
10        # Snip...
11
12    def accept(self):
13        """Accept the data provided through the dialog."""
14        self.data = []
15        for field in (self.nameField, self.jobField, self.emailField):
16            if not field.text():
17                QMessageBox.critical(
18                    self,
19                    "Error!",
20                    f"You must provide a contact's {field.objectName()}",
21                )
22                self.data = None  # Reset .data
23                return
24
25            self.data.append(field.text())
26
27        super().accept()

The code within .accept() does the following:

• Line 14 initializes .data to an empty list ([]). This list will store the user’s input data.
• Line 15 defines a for loop that iterates over the three line edits, or fields, in the dialog.
• Lines 16 to 23 define a conditional statement that checks if the user has provided data for each field in the dialog. If not, then the dialog shows an error message that warns the user about the missing data.
• Line 25 adds the user’s input for each field to .data.
• Line 27 calls the superclass’s .accept() slot to provide the standard behavior that closes the dialog after the user clicks OK.

With this code, you’re ready to add a new slot to the contact book’s main window. This slot will launch the dialog, and if the user provides valid input, then the slot will use the model to save the newly added contact to the database.

Launching the Add Contact Dialog

Now that you’ve coded the Add Contact dialog, it’s time to add a new slot to Window so you can launch the dialog by clicking Add and process the user’s input once they click OK.

Go to the definition of Window and add the following code:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/views.py
 3
 4# Snip...
 5class Window(QMainWindow):
 6    # Snip...
 7
 8    def setupUI(self):
 9        # Snip...
10        self.addButton = QPushButton("Add...")
11        self.addButton.clicked.connect(self.openAddDialog)
12        # Snip...
13
14    def openAddDialog(self):
15        """Open the Add Contact dialog."""
16        dialog = AddDialog(self)
17        if dialog.exec() == QDialog.Accepted:
18            self.contactsModel.addContact(dialog.data)
19            self.table.resizeColumnsToContents()

Here’s a summary of what’s happening in the above code:

• Line 11 connects the .clicked() signal of the Add button to the newly created slot, .openAddDialog(). This way, a click on the button will automatically call the slot.
• Line 14 defines the .openAddDialog() slot.
• Line 16 creates an instance of AddDialog.
• Lines 17 to 19 define a conditional statement to check if the dialog was accepted. If so, then line 14 calls .addContact() on the data model with the dialog’s .data attribute as an argument. The final statement in the if code block resizes the table view to fit the size of its updated content.

Now that you have a way to launch the Add Contact dialog and to process its data, you need to provide the code for .addContact() in your data model. That’s a topic for the next section.

Processing the Add Dialog’s Data in the Model

In this section, you’ll add a method called .addContact() to your data model, ContactsModel. Open model.py in your code editor, go to the definition of ContactsModel, and add the following code:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/model.py
 3
 4# Snip...
 5class ContactsModel:
 6    # Snip...
 7
 8    def addContact(self, data):
 9        """Add a contact to the database."""
10        rows = self.model.rowCount()
11        self.model.insertRows(rows, 1)
12        for column, field in enumerate(data):
13            self.model.setData(self.model.index(rows, column + 1), field)
14        self.model.submitAll()
15        self.model.select()

Inside .addContact(), the code does the following:

• Line 10 gets the current number of rows in the data model.
• Line 11 inserts a new row at the end of the data model.
• Lines 12 and 13 run a for loop that inserts every item in data into the corresponding cell in the data model. To do this, line 9 calls .setData() on the model, with the index of the cell and the current data field as arguments.
• Line 14 submits the changes to the database by calling .submitAll() on the model.
• Line 15 reloads the data from the database into the model.

If you run the application with these new additions, then you’ll get the following behavior:

Now when you click Add, the Add Contact dialog appears on your screen. You can use the dialog to provide the required information for a new contact and to add the contact to the database by clicking OK.

Deleting Selected Contacts

To remove a single contact from the contact database, you need to select the desired contact in the table view on the contact book’s main window. Once you’ve selected the contact, you can click Delete to perform the operation on the database.

Go to the model.py module and add the following code to implement .deleteContact() inside ContactsModel:

# -*- coding: utf-8 -*-
# rpcontacts/model.py

# Snip...
class ContactsModel:
    # Snip...

    def deleteContact(self, row):
        """Remove a contact from the database."""
        self.model.removeRow(row)
        self.model.submitAll()
        self.model.select()

This method has three lines of code. The first line removes the selected row. The second line submits the change to the database. Finally, the third line reloads the data into the model.

Next, get back to the views.py module and add the code behind the Delete button in Window:

# -*- coding: utf-8 -*-
# rpcontacts/views.py

# Snip...
class Window(QMainWindow):
    # Snip...

    def setupUI(self):
        """Setup the main window's GUI."""
        # Snip...
        self.deleteButton = QPushButton("Delete")
        self.deleteButton.clicked.connect(self.deleteContact)
        # Snip...

    def deleteContact(self):
        """Delete the selected contact from the database."""
        row = self.table.currentIndex().row()
        if row < 0:
            return

        messageBox = QMessageBox.warning(
            self,
            "Warning!",
            "Do you want to remove the selected contact?",
            QMessageBox.Ok | QMessageBox.Cancel,
        )

        if messageBox == QMessageBox.Ok:
            self.contactsModel.deleteContact(row)

In the first highlighted line, you connect the .clicked() signal of the Delete button to the .deleteContact() slot. This connection triggers a call to .deleteContact() every time the user clicks the button.

In .deleteContact(), you first get the index of the currently selected row in the table view. The if statement checks if the index is lower than 0, which would mean that there are no contacts in the table view. If so, then the method returns immediately without performing any further actions.

Then the method shows a warning message confirming that the user wants to delete the selected contact. If the user accepts the operation, then .deleteContact(row) gets called. In this case, row represents the index of the currently selected row in the table.

After these additions, you can run the application again to get the following behavior:

Now when you select a contact from the table view and click Delete, you’re presented with a warning message. If you click the message dialog’s OK button, then the application removes the selected contact from the database, updating the table view accordingly.

Clearing the Contact Database

To remove all the contacts from the database, you’ll start by adding a method called .clearContacts() to ContactsModel. Open your model.py module and add the following method at the end of the class:

 1# -*- coding: utf-8 -*-
 2# rpcontacts/model.py
 3
 4# Snip...
 5class ContactsModel:
 6    # Snip...
 7
 8    def clearContacts(self):
 9        """Remove all contacts in the database."""
10        self.model.setEditStrategy(QSqlTableModel.OnManualSubmit)
11        self.model.removeRows(0, self.model.rowCount())
12        self.model.submitAll()
13        self.model.setEditStrategy(QSqlTableModel.OnFieldChange)
14        self.model.select()

Here’s what each line of code does:

• Line 10 sets the data model’s .editStrategy property to QSqlTableModel.OnManualSubmit. This allows you to cache all the changes until you call .submitAll() later on. You need to do this because you’re changing several rows at the same time.
• Line 11 removes all the rows from the model.
• Line 12 saves changes to the database.
• Line 13 resets the model’s .editStrategy property to its original value, QSqlTableModel.OnFieldChange. If you don’t reset this property to its original value, then you won’t be able to update the contacts directly in the table view.
• Line 14 reloads the data into the model.

Once you’ve coded .clearContacts(), you can get back to the views.py file and update Window with the following code:

# -*- coding: utf-8 -*-
# rpcontacts/views.py

# Snip...
class Window(QMainWindow):
    # Snip...

    def setupUI(self):
        """Setup the main window's GUI."""
        # Snip...
        self.clearAllButton = QPushButton("Clear All")
        self.clearAllButton.clicked.connect(self.clearContacts)
        # Snip...

    def clearContacts(self):
        """Remove all contacts from the database."""
        messageBox = QMessageBox.warning(
            self,
            "Warning!",
            "Do you want to remove all your contacts?",
            QMessageBox.Ok | QMessageBox.Cancel,
        )

        if messageBox == QMessageBox.Ok:
            self.contactsModel.clearContacts()

The first highlighted line in this code connects the .clicked() signal of the Clear All button to the .clearContacts() slot below.

In .clearContacts(), you first create a message dialog, messageBox, to ask the user to confirm the removing operation. If the user confirms the operation by clicking OK, then .clearContacts() gets called on the model to remove all the contacts from the database:

That’s it! With this last piece of code, your contact book application is complete. The application provides features that allow your users to display, add, update, and remove contacts from the database.