QlineEdit单行文本框

限制只能输入英文

setAttribute(Qt.WA_InputMethodEnabled,False)

回车功能

    @pyqtSlot()
    def on_username_returnPressed(self):
        if self.username.hasFocus():
            self.password.selectAll()
            self.password.setFocus()

或者 self.username.returnPressed.connect(self.on_username_returnPressed)