What is the easiest way to get all strings that do not start with a character?

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? Thanks in advance for the help.

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.

Answer 2

Here is a nice one-liner, which is very close to natural language.

String definition:

StringList = [ '__one', '__two', 'three', 'four' ] 

Code which performs the deed:

BetterStringList = [ p for p in StringList if not(p.startswith('__'))]