blank lines representation in python

[micklee74 at hotmail.com]

hi
what is the correct way to represent blank lines in python (while
iterating a file) without regexp? I know one way is to use
re.search((line,r'^$') to grab a blank line, but i wanna try not to use
regexp...
is it
1) if line == ''": dosomething()  (this also means EOF right? )
2) if line is None: dosomething()
3) if not line: dosomething()
thanks