[FIXED] QTableWidget- automatic formula driven cell

Issue

Is it possible to make one cell a formula driven cell and have it update automatically? Similar to Excel.

For example, I want user to fill out two cells, and then a third cell will automatically divide when user fills both cells. I'd like it to be NOT connected to a button.

QTable Screenshot

Code for TableWidget:

self.tableWidget = {}
for i in range(int(self.numberLine.text())):
    self.tableWidget[i] = QTableWidget()
    self.tableWidget[i].setRowCount(5)
    self.tableWidget[i].setColumnCount(3)
    self.tableWidget[i].setHorizontalHeaderLabels(['OEM (Case {})'.format(i+1), 'ZVI (Case {})'.format (i+1), 'Improvement % '])
    self.tableWidget[i].setVerticalHeaderLabels(['Flow (MMSCFD)', 'HP', 'Specific Power (HP/MMSCFD)', 'Discharge Temp (F)', ''])
    self.tableWidget[i].setFixedSize(QtCore.QSize(480, 180))
    self.gridLayout_14.addWidget(self.tableWidget[i])

Solution

An elegant solution is to create a custom class that inherits from QTableWidget, where you connect the itemChanged signal, this is issued each time the cell changes value (this returns the changed item but will use it only to verify that the default columns are the ones have been changed).

In addition to not having problems that the user places different values to a floating we will use a QDoubleValidator, for that we create a custom QItemDelegate.

class FloatDelegate(QItemDelegate):
    def __init__(self, _from, _to, _n_decimals, parent=None):
        QItemDelegate.__init__(self, parent=parent)
        self._from = _from
        self._to = _to
        self._n_decimals = _n_decimals

    def createEditor(self, parent, option, index):
        lineEdit = QLineEdit(parent)
        _n_decimals = 2
        validator = QDoubleValidator(self._from, self._to, self._n_decimals, lineEdit)
        lineEdit.setValidator(validator)
        return lineEdit


class CustomTableWidget(QTableWidget):
    _from = 0
    _to = 10**5
    _n_decimals = 2
    def __init__(self, i,  parent=None):
        QTableWidget.__init__(self, 5, 3, parent=parent)
        self.setItemDelegate(FloatDelegate(self._from, self._to, self._n_decimals, self))
        self.setHorizontalHeaderLabels(['OEM (Case {})'.format(i+1), 'ZVI (Case {})'.format (i+1), 'Improvement % '])
        self.setVerticalHeaderLabels(['Flow (MMSCFD)', 'HP', 'Specific Power (HP/MMSCFD)', 'Discharge Temp (F)', ''])
        self.setFixedSize(QSize(480, 180))
        self.itemChanged.connect(self.onItemChanged)

    def onItemChanged(self, item):
        # items (2, 0) = (1, 0) / (0, 0)
        if item.column() == 0 and (item.row() == 0 or item.row()==1):
            num = self.item(1, 0)
            den = self.item(0, 0)
            if num and den:
                resp = float(num.data(Qt.DisplayRole))/float(den.data(Qt.DisplayRole))
                rest_string = str(round(resp, self._n_decimals))
                it = QTableWidgetItem(rest_string, QTableWidgetItem.Type)
                self.setItem(2, 0, it)

Example:

class Widget(QWidget):
    def __init__(self, parent=None):
        QWidget.__init__(self, parent=parent)
        self.setLayout(QGridLayout())
        for i in range(2):
            self.layout().addWidget(CustomTableWidget(i))

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Widget()
    window.show()
    sys.exit(app.exec_())

In your case:

self.tableWidget = {}
for i in range(int(self.numberLine.text())):
    self.tableWidget[i] = CustomTableWidget(i)
    self.gridLayout_14.addWidget(self.tableWidget[i])

Another option instead of using validators, we can change the QLineEdit to QDoubleSpinBox.

def createEditor(self, parent, option, index):
    w = QDoubleSpinBox(parent)
    _n_decimals = 2
    w.setMinimum(self._from)
    w.setMaximum(self._to)
    w.setDecimals(self._n_decimals)
    return w

Answered By - eyllanesc