spliting on ":"

[fileexit]

> yyy
> yyy
> yyy
> xxx.xxx.xxx.xxx
> xxx.xxx.xxx.xxx

of course you will get this result...

inside the loop, when line="xxx.xxx.xxx.xxx:yyy"
line.split(":") will give a list ["xxx.xxx.xxx.xxx", "yyy"], and
element -1 will be "yyy"

but when line="xxx.xxx.xxx.xxx"
line.split(":") will give a list ["xxx.xxx.xxx.xxx"], and element -1
will be "xxx.xxx.xxx.xxx"

So the result is very very normal