Add combobox to horizontal header in QTableWidget

Question

I want to create a table in PyQt5 that has a combobox in each column header. When I try to do it, the following error is returned:

TypeError: setHorizontalHeaderItem(self, int, QTableWidgetItem): argument 2 has unexpected type 'QComboBox'

Apparently the function setHorizontalHeaderItem() doesn't accept widgets as items. So is there a way to achieve this? If not, I would settle with putting the comboboxes above the headers, but they should be aligned with the size of each column, even if the user changes the width with the mouse. I don't know if this is possible either.

My code:

from PyQt5 import QtWidgets 
import numpy as np

class App(QtWidgets.QWidget):
    def __init__(self):
        super(App,self).__init__()
        self.data = np.random.rand(5,5)
        self.createTable()
        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.table) 
        self.setLayout(self.layout) 
        self.showMaximized()

    def createTable(self):
        self.header = []
        self.table = QtWidgets.QTableWidget(len(self.data), len(self.data[0]))
        for i in range(len(self.data[0])):
            self.header.append(QtWidgets.QComboBox())
            self.header[-1].addItem('Variable')
            self.header[-1].addItem('Timestamp')
            self.table.setHorizontalHeaderItem(i,self.header[-1])
        for i in range(len(self.data)):
            for j in range(len(self.data[0])):
                self.table.setItem(i,j,QtWidgets.QTableWidgetItem(str(self.data[i][j])))

if __name__ == '__main__':
    app = QtWidgets.QApplication([])
    ex = App()
    app.exec_()

Answer 1

QHeaderView does not support widgets as items so you must create a custom header as I show below:

from PyQt5 import QtCore, QtWidgets 
import numpy as np

class HorizontalHeader(QtWidgets.QHeaderView):
    def __init__(self, values, parent=None):
        super(HorizontalHeader, self).__init__(QtCore.Qt.Horizontal, parent)
        self.setSectionsMovable(True)
        self.comboboxes = []
        self.sectionResized.connect(self.handleSectionResized)
        self.sectionMoved.connect(self.handleSectionMoved)

    def showEvent(self, event):
        for i in range(self.count()):
            if i < len(self.comboboxes):
                combo = self.comboboxes[i]
                combo.clear()
                combo.addItems(["Variable", "Timestamp"])
            else:
                combo = QtWidgets.QComboBox(self)
                combo.addItems(["Variable", "Timestamp"])
                self.comboboxes.append(combo)

            combo.setGeometry(self.sectionViewportPosition(i), 0, self.sectionSize(i)-4, self.height())
            combo.show()

        if len(self.comboboxes) > self.count():
            for i in range(self.count(), len(self.comboboxes)):
                self.comboboxes[i].deleteLater()

        super(HorizontalHeader, self).showEvent(event)

    def handleSectionResized(self, i):
        for i in range(self.count()):
            j = self.visualIndex(i)
            logical = self.logicalIndex(j)
            self.comboboxes[i].setGeometry(self.sectionViewportPosition(logical), 0, self.sectionSize(logical)-4, self.height())

    def handleSectionMoved(self, i, oldVisualIndex, newVisualIndex):
        for i in range(min(oldVisualIndex, newVisualIndex), self.count()):
            logical = self.logicalIndex(i)
            self.comboboxes[i].setGeometry(self.ectionViewportPosition(logical), 0, self.sectionSize(logical) - 5, height())

    def fixComboPositions(self):
        for i in range(self.count()):
            self.comboboxes[i].setGeometry(self.sectionViewportPosition(i), 0, self.sectionSize(i) - 5, self.height())

class TableWidget(QtWidgets.QTableWidget):
    def __init__(self, *args, **kwargs):
        super(TableWidget, self).__init__(*args, **kwargs)
        header = HorizontalHeader(self)
        self.setHorizontalHeader(header)

    def scrollContentsBy(self, dx, dy):
        super(TableWidget, self).scrollContentsBy(dx, dy)
        if dx != 0:
            self.horizontalHeader().fixComboPositions()


class App(QtWidgets.QWidget):
    def __init__(self):
        super(App,self).__init__()
        self.data = np.random.rand(10, 10)
        self.createTable()
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.table) 
        self.showMaximized()

    def createTable(self):
        self.header = []
        self.table = TableWidget(*self.data.shape)
        for i, row_values in enumerate(self.data):
            for j, value in enumerate(row_values):
                self.table.setItem(i, j, QtWidgets.QTableWidgetItem(str(value)))

if __name__ == '__main__':
    import sys

    app = QtWidgets.QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())