**Course Title:** PyQt6 Application Development **Section Title:** Understanding the Model-View-Controller (MVC) Pattern **Topic:** Working with models: QAbstractListModel, QAbstractTableModel **Overview** In the previous topic, we introduced the Model-View-Controller (MVC) pattern, a fundamental concept in software design that separates an application's data, presentation, and control logic into three interconnected components. In this topic, we'll delve into the world of models, specifically focusing on QAbstractListModel and QAbstractTableModel. These two abstract classes provide the foundation for creating custom data models in PyQt6. **QAbstractListModel** QAbstractListModel is the base class for models that represent a collection of data as a list of items. It provides a common interface for accessing and manipulating the data, allowing views to interact with the model without knowing its internal implementation. **Key Features of QAbstractListModel:** * **rowCount():** Returns the number of items in the list. * **data():** Returns the data for a specific item, given its row index. * **setData():** Sets the data for a specific item, given its row index and new value. * **insertRows():** Inserts new rows into the list. * **removeRows():** Removes rows from the list. **Example: Creating a Custom List Model** Let's create a simple list model that stores a list of strings: ```python import sys from PyQt6.QtCore import QAbstractListModel, Qt from PyQt6.QtWidgets import QApplication, QListView class StringListModel(QAbstractListModel): def __init__(self, strings, parent=None): super().__init__(parent) self._strings = strings def rowCount(self, parent=None): return len(self._strings) def data(self, index, role=Qt.ItemDataRole.DisplayRole): if role == Qt.ItemDataRole.DisplayRole: return self._strings[index.row()] return None if __name__ == "__main__": app = QApplication(sys.argv) strings = ["Apple", "Banana", "Orange"] model = StringListModel(strings) view = QListView() view.setModel(model) view.show() sys.exit(app.exec()) ``` **QAbstractTableModel** QAbstractTableModel is the base class for models that represent data as a two-dimensional table of items. It provides a common interface for accessing and manipulating the data, allowing views to interact with the model without knowing its internal implementation. **Key Features of QAbstractTableModel:** * **rowCount():** Returns the number of rows in the table. * **columnCount():** Returns the number of columns in the table. * **data():** Returns the data for a specific item, given its row and column indices. * **setData():** Sets the data for a specific item, given its row and column indices and new value. * **insertRows():** Inserts new rows into the table. * **removeRows():** Removes rows from the table. * **insertColumns():** Inserts new columns into the table. * **removeColumns():** Removes columns from the table. **Example: Creating a Custom Table Model** Let's create a simple table model that stores a list of dictionaries, where each dictionary represents a row in the table: ```python import sys from PyQt6.QtCore import QAbstractTableModel, Qt from PyQt6.QtWidgets import QApplication, QTableView class TableModel(QAbstractTableModel): def __init__(self, data, parent=None): super().__init__(parent) self._data = data def rowCount(self, parent=None): return len(self._data) def columnCount(self, parent=None): return len(self._data[0].keys()) def data(self, index, role=Qt.ItemDataRole.DisplayRole): if role == Qt.ItemDataRole.DisplayRole: row = index.row() column = index.column() key = list(self._data[0].keys())[column] return self._data[row][key] return None if __name__ == "__main__": app = QApplication(sys.argv) data = [ {"Name": "John", "Age": 25}, {"Name": "Jane", "Age": 30}, {"Name": "Bob", "Age": 35} ] model = TableModel(data) view = QTableView() view.setModel(model) view.show() sys.exit(app.exec()) ``` **Conclusion** In this topic, we explored the QAbstractListModel and QAbstractTableModel classes, which provide the foundation for creating custom data models in PyQt6. We created simple examples of list and table models to demonstrate how to use these classes. Remember to keep your models separate from your views and controllers, following the principles of the MVC pattern. **What's Next?** In the next topic, we'll cover data binding between models and views, which is an essential aspect of PyQt6 programming. We'll explore how to use QDataWidgetMapper and QDataWidgetDelegate to bind data from a model to a view. **Comments and Questions** If you have any comments or questions regarding this topic, please leave a comment below.