pyqt5通過文本對話框打開文件

點擊按鈕，打開文本對話框，找一人文件，打開並顯示內容                                                                                                                                                                                     

                                                                                                                                                                                              QFIleDialog

                                                                

def openfile(self):
    filename,_ = QFileDialog.getOpenFileName(self);
    text=open(filename,'r').read()
    self.textEdit.setText(text)

我用QFile,QTextStream,QIODevice做了半天也沒做出來，改用python自帶的文件操作命令做了出來。