How do I tell the difference between the end of a text file, and an empty line in a text file?

[walterbyrd]

Python's lack of an EOF character is giving me a hard time.

I've tried:

-----
s = f.readline()
while s:
.
.
s = f.readline()
--------

and

-------
s = f.readline()
while s != ''
.
.
s = f.readline()
-------


In both cases, the loop ends as soon it encounters an empty line in
the file, i.e.


xxxxxxxxxx
xxxxxxxxxxx
xxxxxxx
                          < - - -  loop end here
xxxxxxxxxxxxxx
xxxxxxxxxx
x
                           < ---- loop should end here