Ошибка сохранения файла

import sys
from PyQt5.QtWidgets import (QMainWindow, QTextEdit,
    QAction, QFileDialog, QApplication)
from PyQt5.QtGui import QIcon


class Example(QMainWindow):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        self.textEdit = QTextEdit()
        self.setCentralWidget(self.textEdit)
        self.statusBar()

        openFile = QAction(QIcon('open.png'), 'Open', self)
        openFile.setShortcut('Ctrl+O')
        openFile.setStatusTip('Open new File')
        openFile.triggered.connect(self.showDialog)

        saveFile = QAction(QIcon('save.png'), 'Save', self)
        saveFile.setShortcut('Ctrl+S')
        saveFile.setStatusTip('Save this shit')
        saveFile.triggered.connect(self.showDialog2)

        menubar = self.menuBar()
        fileMenu = menubar.addMenu('&File')
        fileMenu.addAction(openFile)
        fileMenu.addAction(saveFile)

        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('File dialog')
        self.show()


    def showDialog(self):

        fname = QFileDialog.getOpenFileName(self, 'Open file', '/home')[0]

        f = open(fname, 'r')

        with f:
            data = f.read()
            self.textEdit.setText(data)
            
    def showDialog2(self):

        fname = QFileDialog.getSaveFileName(self, 'Save file', '/home')

        f = open("fname.txt", 'w')

        with f:
            data = f.write(str(self))
            self.textEdit.setText(data)
            
    


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())