有多个mxd文件 每个mxd都包含数据驱动页面 如何批量导出图片？

import arcpy

mxd = arcpy.mapping.MapDocument(r"C:\Project\ParcelAtlas.mxd")

for pageNum in range(1, mxd.dataDrivenPages.pageCount + 1):

    mxd.dataDrivenPages.currentPageID = pageNum

    print "Exporting page {0} of {1}".format(str(mxd.dataDrivenPages.currentPageID), str(mxd.dataDrivenPages.pageCount))

    arcpy.mapping.ExportToPNG(mxd, r"C:\Project\OutPut\ParcelAtlas_Page" + str(pageNum) + ".png")

del mxd

import arcpy,os

path = r"C:\mxds"

for root,dirs,files in os.walk(path):

    for filename in files:

        basename,extension = os.path.splitext(filename)

        if extension == ".mxd": 

            print "MXD:" + filename + "\n"

import arcpy,os

path = r"C:"

for root,dirs,files in os.walk(path):

    for filename in files:

        basename,extension = os.path.splitext(filename)

        if extension == ".mxd":     

            print "MXD:" + filename + "\n"

            fullpath = os.path.join(root,filename)

            mxd = arcpy.mapping.MapDocument(fullpath)

            for pageNum in range(1, mxd.dataDrivenPages.pageCount + 1):

                mxd.dataDrivenPages.currentPageID = pageNum

                print "Exporting page {0} of {1}".format(str(mxd.dataDrivenPages.currentPageID), str(mxd.dataDrivenPages.pageCount))

                arcpy.mapping.ExportToPNG(mxd, r"C:\Project\OutPut\ParcelAtlas_Page" + str(pageNum) + ".png")

            del mxd