Question

I am trying to parse about 20 million lines from a text file and am looking for a way to do some further manipulations on lines that do not start with question marks. I would like a solution that does not use regex matching. What I would like to do is something like this:

for line in x:
    header = line.startswith('?')
if line.startswith() != header:
        DO SOME STUFF HERE

I realize the startswith method takes one argument, but is there any simple solution to get all lines from a line that DO NOT start with a question mark?

Answer 1

Use generator expressions, the best way I think.

for line in (line for line in x if not line.startswith('?')):
    DO_STUFF

Or your way:

for line in x:
    if line.startswith("?"):
        continue
    DO_STUFF

Or:

for line in x:
    if not line.startswith("?"):
        DO_STUFF

It is really up to your programming style. I prefer the first one, but maybe second one seems simplier. But I don’t really like third one because of a lot of indentation.