Question

How would one write a regular expression to use in Python to split paragraphs?

A paragraph is defined by two line breaks (\n). But one can have any amount of spaces/tabs together with the line breaks, and it still should be considered as a paragraph.

I am using Python, so the solution can use Python’s regular expression syntax which is extended. (can make use of (?P...) stuff)

Examples:

the_str = 'paragraph1\n\nparagraph2' # Splitting should yield ['paragraph1', 'paragraph2']  the_str = 'p1\n\t\np2\t\n\tstill p2\t   \n     \n\tp3' # Should yield ['p1', 'p2\t\n\tstill p2', 'p3']  the_str = 'p1\n\n\n\tp2' # Should yield ['p1', '\n\tp2'] 

The best I could come with is: r'[ \t\r\f\v]*\n[ \t\r\f\v]*\n[ \t\r\f\v]*', i.e.

import re paragraphs = re.split(r'[ \t\r\f\v]*\n[ \t\r\f\v]*\n[ \t\r\f\v]*', the_str) 

But that is ugly. Is there anything better?

Suggestions rejected:

r'\s*?\n\s*?\n\s*?' -> That would make example 2 and 3 fail, since \s includes \n, so it would allow paragraph breaks with more than 2 \ns.

Answer 1

Unfortunately there’s no nice way to write ‘space but not a newline’.

I think the best you can do is add some space with the x modifier and try to factor out the ugliness a bit, but that’s questionable: (?x) (?: [ \t\r\f\v]*? \n ){2} [ \t\r\f\v]*?

You could also try creating a subrule just for the character class and interpolating it three times.