第三个参数如下面的函数定义report，urlretrieve下载文件时会实时回调report函数，显示下载进度
def report(count, blockSize, totalSize):
percent = int(count*blockSize*100/totalSize)
sys.stdout.write("\r%d%%" % percent + ' complete')
sys.stdout.flush()
sys.stdout.write('\rFetching ' + name + '...\n')
urllib.urlretrieve(getFile, saveFile, reporthook=report)
sys.stdout.write("\rDownload complete, saved as %s" % (fileName) + '\n\n')
sys.stdout.flush()
