python文件操作--指定行下一行加入指定内容

fileold = open("/etc/cluster/cluster.conf", "rb+")
configfile_list = fileold.readlines()
fileold.close()
print "length of old cluster.conf:",configfile_list.__len__()
tarline=0
for i in range(configfile_list.__len__()):
if configfile_list[i].__contains__("config_version"):
tarline = int(i)+1


print "add addinfo = '''  \n'''
configfile_list.insert(tarline,addinfo)


print "length of cluster.conf after change:",configfile_list.__len__()
filenew= open("/etc/cluster/cluster.conf","wb")
for item in configfile_list:
filenew.write(item)
filenew.close()