PyQt5 Extremely Slow Scrolling on QTableView with

Question

I am creating a table inside of a PyQt5 GUI using QTableView. I have 35 rows and 5 columns from a pandas dataframe. Scrolling and sorting the table is extremely slow (on the order of seconds).

I have already looked for solutions, but most people were having trouble with populating the table. One person suggested using a numpy array, but I did not see any increase in performance.

Here is my code:

def create_table(dataframe):
    table = QTableView()
    tm = TableModel(dataframe)
    table.setModel(tm)

    table.setSelectionBehavior(QAbstractItemView.SelectRows)
    table.resizeColumnsToContents()
    table.resizeRowsToContents()
    table.setSortingEnabled(True)

    return table



class TableModel(QtCore.QAbstractTableModel):

    def __init__(self, data, parent=None):
        QtCore.QAbstractTableModel.__init__(self, parent)
        self._data = data

    def rowCount(self, parent=None):
        return len(self._data.values)

    def columnCount(self, parent=None):
        return self._data.columns.size

    def data(self, index, role=QtCore.Qt.DisplayRole):
        if index.isValid():
            if role == QtCore.Qt.DisplayRole:
                return str(self._data.values[index.row()][index.column()])
        return None

    def headerData(self, rowcol, orientation, role):
        if orientation == QtCore.Qt.Horizontal and role == QtCore.Qt.DisplayRole:
            return self._data.columns[rowcol]
        if orientation == QtCore.Qt.Vertical and role == QtCore.Qt.DisplayRole:
            return self._data.index[rowcol]
        return None

    def flags(self, index):
        flags = super(self.__class__, self).flags(index)
        flags |= QtCore.Qt.ItemIsEditable
        flags |= QtCore.Qt.ItemIsSelectable
        flags |= QtCore.Qt.ItemIsEnabled
        flags |= QtCore.Qt.ItemIsDragEnabled
        flags |= QtCore.Qt.ItemIsDropEnabled
        return flags

    def sort(self, Ncol, order):
        """Sort table by given column number.
        """
        try:
            self.layoutAboutToBeChanged.emit()
            self._data = self._data.sort_values(self._data.columns[Ncol], ascending=not order)
            self.layoutChanged.emit()
        except Exception as e:
            print(e)


table = create_table(dataframe)

There is one question that I found here Slow scrolling with QTableView on other comp where the user has a similar problem, and he/she found out that the "QTableView is refreshing the items at each scroll / appearance of the window, which is obviously the source of the problem." However I don't know if my table has the same issue as that one.

How can I make scrolling and sorting faster for my table? What are the sources of the problem?

Answer 1

The problem is in the rowCount and data methods since you are not using the best functions. In the case of rowCount when using values you are creating a new data that consumes time, in this case use index. And the same in data, you must use iloc():

def rowCount(self, parent=None):
    return len(self._data.index)

# ...

def data(self, index, role=QtCore.Qt.DisplayRole):
    if index.isValid():
        if role == QtCore.Qt.DisplayRole:
            return str(self._data.iloc[index.row(), index.column()])
    return None