PyQt4 怎么设置setStretchFactor

PyQt4 如何设置setStretchFactor
我网上找了一个使用QSpliiter的例子, 里面包含QFrame与QListWidget.
我想要listWidget占25%, frame点75%大小, 请问如何使用setStretchFactor实现?

以下是代码:

import sys


from PyQt4.QtCore import *

from PyQt4.QtGui import *


QTextCodec.setCodecForTr(QTextCodec.codecForName("utf-8"))


class StockDialog(QDialog):

    def __init__(self, parent=None):

        super(StockDialog, self).__init__(parent)

        self.setWindowTitle(self.tr("综合布局实例"))

        

        mainSplitter = QSplitter(Qt.Horizontal)

        mainSplitter.setOpaqueResize(True)

        

        listWidget = QListWidget(mainSplitter)

        listWidget.insertItem(0, self.tr("个人基本资料"))

        listWidget.insertItem(1, self.tr("联系方式"))

        listWidget.insertItem(2, self.tr("详细信息"))

        

        

        stack = QStackedWidget()

        stack.setFrameStyle(QFrame.Panel|QFrame.Raised)

        

        baseInfo = BaseInfo()

        contact = Contact()

        detail = Detail()

        stack.addWidget(baseInfo)

        stack.addWidget(contact)

        stack.addWidget(detail)

        

        amendPushButton = QPushButton(self.tr("修改"))

        closePushButton = QPushButton(self.tr("关闭"))

        

        buttonLayout = QHBoxLayout()

        buttonLayout.addStretch(1)

        buttonLayout.addWidget(amendPushButton)

        buttonLayout.addWidget(closePushButton)

        

        frame = QFrame(mainSplitter)