python - How to edit column formula so it can be calculated automatically?

Question

I'm making a project using python where it can behave similar to excel, for example when I input some numbers in my cell, it will be automatically calculated in another cell with a defined algorithm.

I have tried implementing some ideas but I get stuck. I can only do simple calculations like adittion and multiplication. I have a problem when I try to edit the code to allow it to do any form of complex calculation.

...

def print_it(self,no):

        if no.column()==2:
            return
        try:
            add = 10
            for column in range(0,2):
                try:
                    add*=int(self.table.item(no.row(),column).text())
                except:
                    pass  
             self.table.setItem(no.row(),2,QtWidgets.QTableWidgetItem(str(add)))
        except Exception as E:
            print(E)

What is the proper way so i can get IKS value when its formula is (X^2 + Y^2) ?

And this is my table

Answer 1

You have to use the itemChanged signal to notify you of the change of some item, then you have to validate if it is the column you want and if so, then make the corresponding calculations.

from PyQt5 import QtCore, QtGui, QtWidgets

# https://stackoverflow.com/a/55523206/6622587
class DoubleDelegate(QtWidgets.QStyledItemDelegate):
    def createEditor(self, parent, option, index):
        editor = QtWidgets.QDoubleSpinBox(parent)
        editor.setFrame(False)
        editor.setMinimum(-1.7976931348623157e308)
        editor.setMaximum(1.7976931348623157e308)
        editor.setSizePolicy(
            QtWidgets.QSizePolicy.Ignored, editor.sizePolicy().verticalPolicy()
        )
        return editor


class EmptyDelegate(QtWidgets.QStyledItemDelegate):
    def createEditor(self, parent, option, index):
        return None


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.tablewidget = QtWidgets.QTableWidget(4, 7)
        self.tablewidget.setHorizontalHeaderLabels(
            ["X", "Y", "f", "A", "IKS", "PGA", "GSS"]
        )
        self.tablewidget.itemChanged.connect(self.on_itemChanged)
        for col in (0, 1):
            delegate = DoubleDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)
        for col in (4,):
            delegate = EmptyDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)

        self.setCentralWidget(self.tablewidget)

    @QtCore.pyqtSlot("QTableWidgetItem*")
    def on_itemChanged(self, item):
        if item.column() in (0, 1):
            self.calculate_iks(item.row())

    def calculate_iks(self, row):
        self.tablewidget.blockSignals(True)
        for col in (0, 1):
            it = self.tablewidget.item(row, col)
            if it is None:
                it = QtWidgets.QTableWidgetItem("0")
                self.tablewidget.setItem(row, col, it)
        self.tablewidget.blockSignals(False)
        it_x = self.tablewidget.item(row, 0)
        it_y = self.tablewidget.item(row, 1)
        x = float(it_x.text())
        y = float(it_y.text())
        iks = x ** 2 + y ** 2
        it_iks = self.tablewidget.item(row, 4)
        if it_iks is None:
            it_iks = QtWidgets.QTableWidgetItem()
            self.tablewidget.setItem(row, 4, it_iks)
        it_iks.setText(str(iks))


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

If you want to calculate gss = iks * pga then you should do the following:

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.tablewidget = QtWidgets.QTableWidget(4, 7)
        self.tablewidget.setHorizontalHeaderLabels(
            ["X", "Y", "f", "A", "IKS", "PGA", "GSS"]
        )
        self.tablewidget.itemChanged.connect(self.on_itemChanged)
        for col in (0, 1, 5):
            delegate = DoubleDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)
        for col in (4, 6,):
            delegate = EmptyDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)

        self.setCentralWidget(self.tablewidget)

    @QtCore.pyqtSlot("QTableWidgetItem*")
    def on_itemChanged(self, item):

        if item.column() in (0, 1):
            self.calculate_iks(item.row())
        elif item.column() in (4, 5):
            self.calculate_gss(item.row())

    # ...

    def calculate_gss(self, row):
        self.tablewidget.blockSignals(True)
        for col in (4, 5, 6):
            it = self.tablewidget.item(row, col)
            if it is None:
                it = QtWidgets.QTableWidgetItem("0")
                self.tablewidget.setItem(row, col, it)
        self.tablewidget.blockSignals(False)
        it_iks = self.tablewidget.item(row, 4)
        it_pga = self.tablewidget.item(row, 5)
        iks = float(it_iks.text())
        pga = float(it_pga.text())
        gss = iks*pga
        it_gss = self.tablewidget.item(row, 6)
        it_gss.setText(str(gss))

I recommend analyzing the solution and not only apply since that is the idea of SO, if it is done in the case of calculating iks and gss you can see that there are many similarities, so that you can restructure the code to do other calculations In a simple way.

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.tablewidget = QtWidgets.QTableWidget(4, 7)
        self.tablewidget.setHorizontalHeaderLabels(
            ["X", "Y", "f", "A", "IKS", "PGA", "GSS"]
        )
        self.tablewidget.itemChanged.connect(self.on_itemChanged)
        for col in (0, 1, 5):
            delegate = DoubleDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)
        for col in (4, 6):
            delegate = EmptyDelegate(self.tablewidget)
            self.tablewidget.setItemDelegateForColumn(col, delegate)

        self.setCentralWidget(self.tablewidget)

        self.calculates = [
            {
                "inputs": (0, 1),  # X, Y
                "output": 4,  # IKS
                "function": lambda X, Y: X ** 2 + Y ** 2,
            },
            {
                "inputs": (4, 5),  # IKS, PGA
                "output": 6,  # GSS
                "function": lambda IKS, PGA: IKS * PGA,
            },
        ]

    @QtCore.pyqtSlot("QTableWidgetItem*")
    def on_itemChanged(self, item):
        for c in self.calculates:
            inputs = c["inputs"]
            output = c["output"]
            function = c["function"]
            if item.column() in inputs:
                self.calculate(item.row(), inputs, output, function)

    def calculate(self, row, inputs, output, function):
        self.tablewidget.blockSignals(True)
        for col in (*inputs, output):
            it = self.tablewidget.item(row, col)
            if it is None:
                it = QtWidgets.QTableWidgetItem("0")
                self.tablewidget.setItem(row, col, it)
        self.tablewidget.blockSignals(False)
        values = [float(self.tablewidget.item(row, i).text()) for i in inputs]
        result = function(*values)
        it_out = self.tablewidget.item(row, output)
        it_out.setText(str(result))