I would stack generator expressions:
with open(filename) as f_in: # All lines including the blank ones lines = (line.rstrip() for line in f_in) lines = (line for line in lines if line) # Non-blank lines
Now, lines is all of the non-blank lines. This will save you from having to call strip on the line twice. If you want a list of lines, then you can just do:
with open(filename) as f_in: lines = (line.rstrip() for line in f_in) # Non-blank lines in a list lines = list(line for line in lines if line)
You can also do it in a one-liner (exluding with statement) but it's no more efficient and harder to read:
with open(filename) as f_in: lines = list(line for line in (l.strip() for l in f_in) if line)
Update:
I agree that this is ugly because of the repetition of tokens. You could just write a generator if you prefer:
def nonblank_lines(f): for l in f: line = l.rstrip() if line: yield line
Then call it like:
with open(filename) as f_in: for line in nonblank_lines(f_in): # Stuff
update 2:
with open(filename) as f_in: lines = filter(None, (line.rstrip() for line in f_in))
and on CPython (with deterministic reference counting)
lines = filter(None, (line.rstrip() for line in open(filename)))
In Python 2 use itertools.ifilter if you want a generator and in Python 3,
just pass the whole thing to list if you want a list.