PyQt4，从PyQt4 Designer运行文件

Question

最近我了解了PyQt4 Designer并决定尝试一下，下面是代码。

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_MainWindow(object):
    def back(self):
        self.webView.back()
    def forword(self):
        self.webView.forward()
    def reload(self):
        self.webView.reload()

    def home(self):
        self.webView.load(QtCore.QUrl("http://www.google.com"))
    def search(self):
        url = self.ln_addressbar.text()
        self.webView.load(QtCore.QUrl(url))
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(770, 475)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.tb_back = QtGui.QToolButton(self.centralwidget)
        self.tb_back.setGeometry(QtCore.QRect(10, 20, 41, 31))
        icon = QtGui.QIcon()
        icon.addPixmap(QtGui.QPixmap(_fromUtf8("icons/back.png")), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.tb_back.setIcon(icon)
        self.tb_back.setIconSize(QtCore.QSize(32, 32))
        self.tb_back.setObjectName(_fromUtf8("tb_back"))
        ############### Event #############################3
        self.tb_back.clicked.connect(self.back)
        ##################################################
        self.tb_reload = QtGui.QToolButton(self.centralwidget)
        self.tb_reload.setGeometry(QtCore.QRect(60, 20, 41, 31))
        icon1 = QtGui.QIcon()
        icon1.addPixmap(QtGui.QPixmap(_fromUtf8("icons/reload.png")), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.tb_reload.setIcon(icon1)
        self.tb_reload.setIconSize(QtCore.QSize(32, 32))
        self.tb_reload.setObjectName(_fromUtf8("tb_reload"))
        ############### Event #############################3
        self.tb_reload.clicked.connect(self.reload)
        ##################################################
        self.tb_forword_2 = QtGui.QToolButton(self.centralwidget)
        self.tb_forword_2.setGeometry(QtCore.QRect(110, 20, 41, 31))
        icon2 = QtGui.QIcon()
        icon2.addPixmap(QtGui.QPixmap(_fromUtf8("icons/forword.png")), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.tb_forword_2.setIcon(icon2)
        self.tb_forword_2.setIconSize(QtCore.QSize(32, 32))
        self.tb_forword_2.setObjectName(_fromUtf8("tb_forword_2"))
        ############### Event #############################3
        self.tb_forword_2.clicked.connect(self.forword)
        ##################################################
        self.tb_home = QtGui.QToolButton(self.centralwidget)
        self.tb_home.setGeometry(QtCore.QRect(160, 20, 41, 31))
        icon3 = QtGui.QIcon()
        icon3.addPixmap(QtGui.QPixmap(_fromUtf8("icons/home.png")), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.tb_home.setIcon(icon3)
        self.tb_home.setIconSize(QtCore.QSize(32, 32))
        self.tb_home.setObjectName(_fromUtf8("tb_home"))
        ############### Event #############################3
        self.tb_home.clicked.connect(self.home)
        ##################################################
        self.ln_addressbar = QtGui.QLineEdit(self.centralwidget)
        self.ln_addressbar.setGeometry(QtCore.QRect(210, 20, 491, 31))
        self.ln_addressbar.setObjectName(_fromUtf8("ln_addressbar"))


        self.tb_search = QtGui.QToolButton(self.centralwidget)
        self.tb_search.setGeometry(QtCore.QRect(710, 20, 41, 31))
        icon4 = QtGui.QIcon()
        icon4.addPixmap(QtGui.QPixmap(_fromUtf8("icons/search.png")), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.tb_search.setIcon(icon4)
        self.tb_search.setIconSize(QtCore.QSize(32, 32))
        self.tb_search.setObjectName(_fromUtf8("tb_search"))
        ############### Event #############################3
        self.tb_search.clicked.connect(self.search)
        ##################################################
        self.webView = QtWebKit.QWebView(self.centralwidget)
        self.webView.setGeometry(QtCore.QRect(0, 60, 771, 421))
        self.webView.setUrl(QtCore.QUrl(_fromUtf8("about:blank")))
        self.webView.setObjectName(_fromUtf8("webView"))
        MainWindow.setCentralWidget(self.centralwidget)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.tb_back.setText(_translate("MainWindow", "...", None))
        self.tb_reload.setText(_translate("MainWindow", "...", None))
        self.tb_forword_2.setText(_translate("MainWindow", "...", None))
        self.tb_home.setText(_translate("MainWindow", "...", None))
        self.tb_search.setText(_translate("MainWindow", "...", None))

from PyQt4 import QtWebKit

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_())

但是，当我尝试运行它时，将.ui文件转换为.py后，我收到此错误：

File "C:\Users\###-_000\Desktop\browser.py", line 3, in <module>
    from PyQt4 import QtCore, QtGui
ImportError: cannot import name 'QtCore'

提前致谢！