python - 名称错误 : name 'x' is not defined

Question

当我运行我的代码(并按下我制作的 GUI 上的启用按钮)时，我得到了

NameError: name 'stu' is not defined

错误。我绞尽脑汁想弄清楚为什么会这样，但我做不到，所以我决定将它发布到 Stackoverflow 上；-)。

我猜它必须对全局变量和局部变量做一些事情，但无论我把 global 放在哪里，它仍然无法运行。

Windows 10 专业版 64 位 Python 3.4(Annaconda3 发行版)。

我希望您能提供帮助，如果您决定提供帮助，请提供某种解释或来源，这样我就不会再次陷入这个愚蠢的问题。

谢谢!

完整代码如下:

# -*- coding: utf-8 -*-

from PyQt4 import QtCore, QtGui
from os import getcwd, remove, system, environ
from os.path import isfile
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 MyPopup(QtGui.QDialog):

    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.setWindowTitle(_translate("MyPopup", "About", None))
        icon = QtGui.QIcon()
        icon.addPixmap(
            QtGui.QPixmap(
                _fromUtf8("./about.png")),
            QtGui.QIcon.Normal,
            QtGui.QIcon.Off)
        self.setWindowIcon(icon)
        resolution = QtGui.QDesktopWidget().screenGeometry()
        self.move((resolution.width() / 2) - (self.frameSize().width() / 2),
                  (resolution.height() / 2) - (self.frameSize().height() / 2))
        pic = QtGui.QLabel(self)
        pic.setGeometry(20, 20, 128, 128)
        pic.setPixmap(QtGui.QPixmap(getcwd() + "/icon.gif"))
        self.setMinimumSize(QtCore.QSize(420, 300))
        self.setMaximumSize(QtCore.QSize(420, 300))
        labele = QtGui.QLabel(self)
        labele.setGeometry(QtCore.QRect(158, 20, 2000, 50))
        font = QtGui.QFont()
        font.setPointSize(26)
        labele.setText(_translate("MyPopup", "NoSleep", None))
        labele.setFont(font)
        # self.setWindowFlags(Qt.FramelessWindowHint)
        labelel = QtGui.QLabel(self)
        labelel.setGeometry(QtCore.QRect(158, 70, 2000, 25))
        font = QtGui.QFont()
        font.setPointSize(16)
        labelel.setText(_translate("MyPopup", "Jan Murić", None))
        labelel.setFont(font)

        labelo = QtGui.QLabel(self)
        labelo.setGeometry(QtCore.QRect(100, 175, 300, 100))
        font = QtGui.QFont()
        font.setPointSize(10)
        labelo.setText(
            _translate(
                "MyPopup",
                "FREEWARE\n\nVersion:   1.0\nE-Mail:        janek.muric@gmail.com",
                None))
        labelo.setFont(font)

        exitButton = QtGui.QPushButton(self)
        exitButton.setGeometry(QtCore.QRect(347, 276, 71, 23))
        exitButton.setText(_translate("MyPopup", "Ok", None))
        exitButton.clicked.connect(self.quit)

    def quit(self):
        self.close()        


class Ui_MainWindow(object):
    user = environ['USERNAME']
    if isfile("C:/Users/"+ user +"/setting.txt") == True:

        f = open("C:/Users/"+ user +"/setting.txt", 'r')
        stu = f.read()
        print(stu) #Print confirms that the variable is sucessfully set
        f.close()
    else:

        f = open("C:/Users/"+ user +"/setting.txt", 'w')
        f.truncate()
        f.write("0")
        f.close()
        stu = 0
        print(stu) #Print confirms that the variable is sucessfully set


    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(363, 199)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.about = QtGui.QPushButton(self.centralwidget)
        self.about.setGeometry(QtCore.QRect(330, 0, 31, 31))
        self.about.setObjectName(_fromUtf8("about"))
        self.groupBox = QtGui.QGroupBox(self.centralwidget)
        self.groupBox.setGeometry(QtCore.QRect(10, 80, 131, 111))
        self.groupBox.setObjectName(_fromUtf8("groupBox"))
        self.chrome = QtGui.QCheckBox(self.groupBox)
        self.chrome.setGeometry(QtCore.QRect(20, 20, 91, 17))
        self.chrome.setChecked(True)
        self.chrome.setObjectName(_fromUtf8("chrome"))
        self.firefox_2 = QtGui.QCheckBox(self.groupBox)
        self.firefox_2.setGeometry(QtCore.QRect(20, 50, 91, 17))
        self.firefox_2.setChecked(True)
        self.firefox_2.setObjectName(_fromUtf8("firefox_2"))
        self.ie = QtGui.QCheckBox(self.groupBox)
        self.ie.setGeometry(QtCore.QRect(20, 80, 101, 17))
        self.ie.setChecked(True)
        self.ie.setObjectName(_fromUtf8("ie"))
        self.enable = QtGui.QPushButton(self.centralwidget)
        self.enable.setGeometry(QtCore.QRect(280, 170, 75, 23))
        self.enable.setObjectName(_fromUtf8("enable"))
        self.startup = QtGui.QCheckBox(self.centralwidget)
        self.startup.setGeometry(QtCore.QRect(160, 170, 101, 17))
        self.startup.setChecked(True)
        self.startup.setObjectName(_fromUtf8("startup"))
        self.display = QtGui.QCheckBox(self.centralwidget)
        self.display.setGeometry(QtCore.QRect(160, 140, 131, 17))
        self.display.setObjectName(_fromUtf8("display"))
        self.label = QtGui.QLabel(self.centralwidget)
        self.label_2 = QtGui.QLabel(self.centralwidget)
        self.label_3 = QtGui.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(10, 0, 271, 71))
        self.label_2.setGeometry(QtCore.QRect(160, 80, 61, 41))
        self.label_3.setGeometry(QtCore.QRect(225, 80, 131, 41))
        self.label.setObjectName(_fromUtf8("label"))
        self.groupBox.raise_()
        self.about.raise_()
        self.enable.raise_()
        self.startup.raise_()
        self.display.raise_()
        self.label.raise_()
        self.icon = QtGui.QIcon()
        self.icon.addPixmap(QtGui.QPixmap(_fromUtf8("./icon.gif")),QtGui.QIcon.Normal,QtGui.QIcon.Off)
        app.setWindowIcon(self.icon)
        self.about.clicked.connect(self.openAbout)
        self.enable.clicked.connect(self.activate)
        MainWindow.setCentralWidget(self.centralwidget)
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "NoSleep", None))
        self.about.setText(_translate("MainWindow", "?", None))
        self.groupBox.setTitle(_translate("MainWindow", "Browsers", None))
        self.chrome.setText(_translate("MainWindow", "Google Chrome", None))
        self.firefox_2.setText(_translate("MainWindow", "Mozilla Firefox", None))
        self.ie.setText(_translate("MainWindow", "Internet Explorer", None))
        self.enable.setText(_translate("MainWindow", "Enable", None))
        self.startup.setText(_translate("MainWindow", "Run on startup", None))
        self.display.setText(_translate("MainWindow", "Disable display timeout ", None))
        self.label_2.setText(_translate("MainWindow", "Status:", None))
        self.label_3.setText(_translate("MainWindow", "Incative", None))
        font = QtGui.QFont()
        font.setPointSize(15)
        palette = QtGui.QPalette()
        palette.setColor(QtGui.QPalette.Foreground, QtCore.Qt.darkRed)
        self.label_3.setPalette(palette)
        self.label_2.setFont(font)
        self.label_3.setFont(font)
        self.label.setText(_translate("MainWindow", "If the program is enabled auto sleep will be disabled\n"
        "if a download is in progess in selected browsers.\n"
        "\n"
        "This program is compatible with Chrome, Firefox and IE.", None))

    def openAbout(self):
        self.w = MyPopup()
        self.w.exec_()


    def activate(self):
        global user
        global stu

        if stu == 0:

            #Setting Visuals
            stu = 1
            f = open("C:/Users/"+ user +"/setting.txt", 'w')
            f.truncate()
            f.write("1")
            f.close()
            self.groupBox.setEnabled(False)
            self.display.setEnabled(False)
            self.startup.setEnabled(False)
            self.enable.setText(_translate("MainWindow", "Disable", None))
            self.label_3.setText(_translate("MainWindow", "Active", None))
            palette = QtGui.QPalette()
            palette.setColor(QtGui.QPalette.Foreground, QtCore.Qt.darkGreen)
            self.label_3.setPalette(palette)

        elif stu == 1:

            #Setting Visuals
            stu = 0
            f = open("C:/Users/"+ user +"/setting.txt", 'w')
            f.truncate()
            f.write("0")
            f.close()
            self.groupBox.setEnabled(True)
            self.display.setEnabled(True)
            self.startup.setEnabled(True)
            self.enable.setText(_translate("MainWindow", "Enable", None))
            self.label_3.setText(_translate("MainWindow", "Inactive", None))
            palette = QtGui.QPalette()
            palette.setColor(QtGui.QPalette.Foreground, QtCore.Qt.darkRed)
            self.label_3.setPalette(palette)

    if stu == 0:
        self.groupBox.setEnabled(False)
        self.display.setEnabled(False)
        self.startup.setEnabled(False)
        self.enable.setText(_translate("MainWindow", "Disable", None))
        self.label_3.setText(_translate("MainWindow", "Active", None))
        palette = QtGui.QPalette()
        palette.setColor(QtGui.QPalette.Foreground, QtCore.Qt.darkGreen)
        self.label_3.setPalette(palette)
    elif stu == 1:
        self.groupBox.setEnabled(True)
        self.display.setEnabled(True)
        self.startup.setEnabled(True)
        self.enable.setText(_translate("MainWindow", "Enable", None))
        self.label_3.setText(_translate("MainWindow", "Inactive", None))
        palette = QtGui.QPalette()
        palette.setColor(QtGui.QPalette.Foreground, QtCore.Qt.darkRed)
        self.label_3.setPalette(palette)
if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

编辑:

糟糕，忘了完整的错误:

Traceback (most recent call last):
  File "C:\Users\Jan\Desktop\output.py", line 180, in activate
    if stu == 0:
NameError: name 'stu' is not defined

Answer 1

stu 是一个类属性，不是全局的。您在类 block 中定义它:

class Ui_MainWindow(object):
    if ...:
        # ...
        stu = f.read()
    else:
        # ...
        stu = 0

您可以在 Ui_MainWindow.activate() 方法中这样处理它:

if Ui_MainWindow.stu == 0:

请注意，您从未将文件内容从字符串转换为整数，因此 stu 很可能设置为 '0' 或 '1' 字符串。您可能希望将字符串转换为整数:

with open("C:/Users/"+ user +"/setting.txt", 'r'):
    try:
        stu = int(f.read())
    except ValueError:
        stu = 0

with 语句负责为您关闭文件。