确定Equals（）是否为覆盖？(Determine if Equals() is an override?)

 您的代码的主要问题是您为StartQT4子类使用了错误的基类。 它应该与Qt Designer中的顶级类匹配，后者是QDialog 。 
 
 您还可以通过将ui直接添加到子类，以及使用新式信号和插槽语法来简化代码。 
 
 有了这些更改，您的代码将如下所示： 
 
import sys
from PyQt4 import QtCore, QtGui
from simpleTextEditor_gui import Ui_simpleTextEditor

class StartQT4(QtGui.QDialog, Ui_simpleTextEditor):
    def __init__(self, parent=None):
        QtGui.QDialog.__init__(self, parent)
        self.setupUi(self)
        # tutaj dajemy wlasne polaczenia slotow
        self.buttonOpen.clicked.connect(self.file_dialog)

    def file_dialog(self):
        fd = QtGui.QFileDialog(self)
        self.filename = fd.getOpenFileName()
        from os.path import isfile
        if isfile(self.filename):
            text = open(self.filename).read()
            self.editorWindow.setText(text)

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = StartQT4()
    myapp.show()
    sys.exit(app.exec_())

The main problem with your code is that you are using the wrong base-class for your StartQT4 subclass. It should match the top-level class from Qt Designer, which is a QDialog.
 
You can also simplify your code a little, by adding the ui directly to your sub-class, and by using new-style signal and slot syntax.
 
With these changes in place, your code would look like this:
 
import sys
from PyQt4 import QtCore, QtGui
from simpleTextEditor_gui import Ui_simpleTextEditor

class StartQT4(QtGui.QDialog, Ui_simpleTextEditor):
    def __init__(self, parent=None):
        QtGui.QDialog.__init__(self, parent)
        self.setupUi(self)
        # tutaj dajemy wlasne polaczenia slotow
        self.buttonOpen.clicked.connect(self.file_dialog)

    def file_dialog(self):
        fd = QtGui.QFileDialog(self)
        self.filename = fd.getOpenFileName()
        from os.path import isfile
        if isfile(self.filename):
            text = open(self.filename).read()
            self.editorWindow.setText(text)

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = StartQT4()
    myapp.show()
    sys.exit(app.exec_())