View Exercise 1 Solution

main.py

import sys

from qtpy.QtWidgets import QApplication

from view import View


def _get_qapplication_instance():
    if app := QApplication.instance():
        return app
    return QApplication(sys.argv)

if __name__ == "__main__" :
    app = _get_qapplication_instance()
    window = View()
    window.show()
    app.exec_()

view.py

from qtpy.QtCore import Qt
from qtpy.QtWidgets import QComboBox, QPushButton, QTableWidget, QTableWidgetItem, QVBoxLayout, QWidget

from typing import Union

TEXT_COLUMN = 0
WIDGET_COLUMN = 1


class View(QWidget):

    def __init__(self, parent: Union[QWidget, None]=None):
        super().__init__(parent)
        self.setWindowTitle("view tutorial")

        grid = QVBoxLayout(self)

        self._table = QTableWidget(self)
        self._table.setRowCount(4)
        self._table.setColumnCount(2)
        grid.addWidget(self._table)

        self._colours = QComboBox()
        options = ["Blue", "Green", "Red"]
        self._colours.addItems(options)

        self._grid_lines = QTableWidgetItem()
        self._grid_lines.setFlags(Qt.ItemIsUserCheckable | Qt.ItemIsEnabled)
        self._grid_lines.setCheckState(Qt.Unchecked)
        self._add_item_to_table("Show grid lines", self._grid_lines, 1)

        freq = QTableWidgetItem("1.0")
        phi = QTableWidgetItem("0.0")

        self._add_widget_to_table("Colour", self._colours, 0)
        self._add_item_to_table("Frequency", freq, 2)
        self._add_item_to_table("Phase", phi, 3)

        self._plot = QPushButton('Add', self)
        self._plot.setStyleSheet("background-color:lightgrey")

        grid.addWidget(self._plot)

        self.setLayout(grid)

    def _set_table_row(self, name: str, row: int) -> None:
        text = QTableWidgetItem(name)
        text.setFlags(Qt.ItemIsEnabled)
        self._table.setItem(row, TEXT_COLUMN, text)

    def _add_widget_to_table(self, name: str, widget: QWidget, row: int) -> None:
        self._set_table_row(name,row)
        self._table.setCellWidget(row, WIDGET_COLUMN, widget)

    def _add_item_to_table(self, name: str, widget: QWidget, row: int) -> None:
        self._set_table_row(name, row)
        self._table.setItem(row, WIDGET_COLUMN, widget)

In the above code the following functions have been added to prevent repetition of code:

• _set_table_row sets the label for the table row

• _add_widget_to_table adds a widget to the table

• _add_item_to_table adds an item to the table (needed because the frequency and phase are items and not widgets)