import sys

from PyQt5 import QtWidgets, QtCore

class MyWidget(QtWidgets.QWidget):

    def __init__(self, i=0):

        super().__init__()

        self.setWindowTitle('窗口 ' + str(i))

        label = QtWidgets.QLabel('标签 ' + str(i))

        layout = QtWidgets.QHBoxLayout(self)

        layout.addWidget(label)

class TestWidget(QtWidgets.QWidget):

    def __init__(self, parent=None):

        super().__init__(parent)

        layout = QtWidgets.QHBoxLayout(self)

        #stack  = QtWidgets.QStackedWidget() # ① Widget

        stack  = QtWidgets.QStackedLayout() # ② Layout

        list   = QtWidgets.QListWidget(self)

        list.setDragEnabled(True)

        list.setDragDropMode(QtWidgets.QAbstractItemView.InternalMove)

        layout.addWidget(list)

        #layout.addWidget(stack) # ① 对应 addWidget

        layout.addLayout(stack) # ② 对应 addLayout

        for i in range(10):

            stack.addWidget(MyWidget(i))

            list.addItem("窗口   %04i" % i)

        list.currentRowChanged.connect(stack.setCurrentIndex)

if __name__ == "__main__":

    app    = QtWidgets.QApplication(sys.argv)

    widget = TestWidget()

    #widget = MyWidget()

    widget.show()

    sys.exit(app.exec_())

        # ... ...

        self.contentsWidget.currentItemChanged.connect(self.changePage)

        #self.contentsWidget.currentRowChanged.connect(self.pagesWidget.setCurrentIndex)

    def changePage(self, current, previous):

        if not current:

            current = previous

        self.pagesWidget.setCurrentIndex(self.contentsWidget.row(current))