python 日志内容提取

xxxxx
yyyyy
start:
start:
hahahaha
end:
start:
hahahahha
end:
ccccccc
kkkkkkk
cdcdcdcd
start:
hahahaha
end:

import re

isfind=False
with open("a.log","r") as f:
    while(1):
        l=f.readline()
        if(not l):
            break
        if(re.match("start:", l)):
            isfind=True
        if(isfind):
            print(l)
            if(re.match("end:", l)):
                isfind=False

start:
start:
hahahaha
end:
start:
hahahahha
end:
start:
hahahaha
end: