spliting on ":"

[s99999999s2003 at yahoo.com]

hi

i have a file with

xxx.xxx.xxx.xxx:yyy
xxx.xxx.xxx.xxx:yyy
xxx.xxx.xxx.xxx:yyy
xxx.xxx.xxx.xxx
xxx.xxx.xxx.xxx
xxx.xxx.xxx.xxx:yyy

i wanna split on ":" and get all the "yyy" and print the whole line out
so i did

print line.split(":")[-1]

but line 4 and 5 are not printed as there is no ":" to split. It should
print a "blank" at least.
how to print out lines 4 and 5 ?
eg output is

yyy
yyy
yyy


yyy

thanks