Сериализация таблицы QTableWidget

from PyQt5.QtWidgets import (QApplication, QGridLayout, 
QWidget, QTableWidget, QTableWidgetItem, QFileDialog,QPushButton)
 
 
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.fname = ''
        self.table = QTableWidget(3,4)
        self.btnLoad = QPushButton("load")
        self.btnSave = QPushButton("Save")
        grid = QGridLayout(self)
        grid.setContentsMargins(1,1,1,1)
        grid.addWidget(self.table,0,0,4,4)
        grid.addWidget(self.btnLoad, 4, 0)
        grid.addWidget(self.btnSave, 4, 1)
        self.btnLoad.clicked.connect(self.on_load)
        self.btnSave.clicked.connect(self.on_save)
        
    def on_load(self):
        fname,_ = QFileDialog.getOpenFileName(self,'Load',self.fname,"*.csv")
        if not fname: return
        self.fname = fname
        with open(fname) as f:
            s = f.read()
        data = [i.split(';') for i in s.strip().split('\n')]
        rows = len(data)
        cols = len(data[0])
        self.table.clear()
        self.table.setRowCount(rows)
        self.table.setColumnCount(cols)
        for row in range(rows):
            for col in range(cols):
                self.table.setItem(row,col,QTableWidgetItem(data[row][col]))
        
 
    def on_save(self):
        fname,_ = QFileDialog.getSaveFileName(self,'Save',self.fname,"*.csv")
        if not fname: return
        self.fname = fname
        f = open(fname,'w')
        for row in range(self.table.rowCount()):
            tmp = []
            for col in range(self.table.columnCount()):
                try: tmp.append(self.table.item(row,col).text())
                except: tmp.append('')
            f.write(';'.join(tmp) + '\n')
        f.close()
        
if __name__ == "__main__":
    import sys
    app = QApplication(sys.argv)
    w = Window()
    w.show()
    sys.exit(app.exec())