Python 关闭对话框时出现了什么错误

我正在学习PyQt，我有一个小应用程序，它似乎可以正常工作，当我点击对话框右上角的X关闭它时。当我这样做并返回控制台时，我看到出现了一个异常，如下所示：

To exit: use 'exit', 'quit', or Ctrl-D.
An exception has occurred, use %tb to see the full traceback.

SystemExit: 0


In [2]: %tb
Traceback (most recent call last):

  File "<ipython-input-1-4524246fa84a>", line 1, in <module>
    runfile('C:/Users/21025/simpleAdder.pyw', wdir='C:/Users/21025')

  File "C:\Users\21035\AppData\Local\Continuum\Anaconda\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 586, in runfile
    execfile(filename, namespace)

  File "C:/Users/21035/simpleAdder.pyw", line 81, in <module>
    sys.exit(app.exec_())

SystemExit: 0

---

如消息所示，代码包括

sys.exit（app.exec_u1;（））

，它将执行GUI，然后调用退出例程。您从一个交互式提示中调用了它，因此它没有退出，而是通知您试图从您调用的对象中退出。如果您希望能够从交互式提示中调用此代码而不出现错误，只需删除退出部分，将

sys.exit（app.exec_（））

更改为

app.exec_（）

以扩展说明：将

sys

想象为Python本身。因此，当您的GUI完成执行时，正如@mdurant所说，您正在告诉python退出它自己。。。然而，你身处一个互动的环境中。如果您是从终端或在独立应用程序中运行，那么这仍然是很好的代码，但是在交互环境中，您试图退出交互环境的核心组件（python），这就是为什么它被认为是错误的原因。

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName(_fromUtf8("Dialog"))
        Dialog.resize(673, 565)
        self.v1Input = QtGui.QLineEdit(Dialog)
        self.v1Input.setGeometry(QtCore.QRect(50, 70, 71, 20))
        self.v1Input.setObjectName(_fromUtf8("v1Input"))
        self.v2Input = QtGui.QLineEdit(Dialog)
        self.v2Input.setGeometry(QtCore.QRect(150, 70, 71, 20))
        self.v2Input.setObjectName(_fromUtf8("v2Input"))
        self.v3Input = QtGui.QLineEdit(Dialog)
        self.v3Input.setGeometry(QtCore.QRect(250, 70, 71, 20))
        self.v3Input.setObjectName(_fromUtf8("v3Input"))
        self.calc_result = QtGui.QLineEdit(Dialog)
        self.calc_result.setGeometry(QtCore.QRect(420, 70, 113, 20))
        self.calc_result.setObjectName(_fromUtf8("calc_result"))
        self.label = QtGui.QLabel(Dialog)
        self.label.setGeometry(QtCore.QRect(60, 50, 46, 13))
        self.label.setObjectName(_fromUtf8("label"))
        self.label_2 = QtGui.QLabel(Dialog)
        self.label_2.setGeometry(QtCore.QRect(160, 50, 46, 13))
        self.label_2.setObjectName(_fromUtf8("label_2"))
        self.label_3 = QtGui.QLabel(Dialog)
        self.label_3.setGeometry(QtCore.QRect(260, 50, 46, 13))
        self.label_3.setObjectName(_fromUtf8("label_3"))
        self.label_4 = QtGui.QLabel(Dialog)
        self.label_4.setGeometry(QtCore.QRect(450, 50, 46, 13))
        self.label_4.setObjectName(_fromUtf8("label_4"))
        self.pushButton = QtGui.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(200, 230, 75, 23))
        self.pushButton.setObjectName(_fromUtf8("pushButton"))

        self.retranslateUi(Dialog)
        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked()")), self.v1Input.clear)
        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked()")), self.v2Input.clear)
        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked()")), self.v3Input.clear)
        QtCore.QMetaObject.connectSlotsByName(Dialog)


    def retranslateUi(self, Dialog):
        Dialog.setWindowTitle(_translate("Dialog", "Dialog", None))
        self.label.setText(_translate("Dialog", "Val 1", None))
        self.label_2.setText(_translate("Dialog", "Val 2", None))
        self.label_3.setText(_translate("Dialog", "Val 3", None))
        self.label_4.setText(_translate("Dialog", "Result", None))
        self.pushButton.setText(_translate("Dialog", "Clear Inputs", None))       


if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    Dialog = QtGui.QDialog()
    ui = Ui_Dialog()
    ui.setupUi(Dialog)
    Dialog.show()
    sys.exit(app.exec_())