这段reduce代码 没一行都是什么意思

import sys
carid=""
count=0
for line in sys.stdin:
line=line.strip()
seg=line.split("\t")
if carid=="":
carid=seg[0]
else:
if carid==seg[0]:
count=count+1
else:
print "%s\t%s" %(carid,count)
count=1
carid=seg[0]
print "%s\t%d" %(carid,count)

carid=""
count=0
for line in sys.stdin: //循环每行
line=line.strip()//去空格
seg=line.split("\t")//以\t分隔为数组
if carid=="":
carid=seg[0]
else:
if carid==seg[0]:
count=count+1
else:
print "%s\t%s" %(carid,count)//格式化输出，cardid和count会替换掉两个%s
count=1
carid=seg[0]
print "%s\t%d" %(carid,count)