How to grep lines between two patterns in a big file with python

Question

I have a very big file, like this:

[PATTERN1]
line1
line2
line3 
...
...
[END PATTERN]
[PATTERN2]
line1 
line2
...
...
[END PATTERN]

I need to extract

Answer 1

Consider:

# hi
# there
# begin
# need
# this
# stuff
# end
# skip
# this

with open(__file__) as fp:
    for line in iter(fp.readline, '# begin\n'):
        pass
    for line in iter(fp.readline, '# end\n'):
        print line

prints "need this stuff"

More flexible (e.g. to allow re pattern matching) is to use itertools drop- and takewhile:

with open(__file__) as fp:
    result = list(itertools.takewhile(lambda x: 'end' not in x, 
        itertools.dropwhile(lambda x: 'begin' not in x, fp)))