CODEWITHSUNDEEP
javascriptregexstring
painhurt
painhurt

Reputation: 23

Splitting a string every n lines using regex

"LINE 1.
LINE 2.
LINE 3.
LINE 4.
LINE 5.
LINE 6."

Suppose i want to split the above string every 3 lines using the split() method, what regex delimiter should i use to produce something like this :

["LINE 1.
LINE 2.
LINE 3.",
"LINE 4.
LINE 5.
LINE 6."]

Upvotes: 0

Views: 2064

Answers (2)

user2692263
user2692263

Reputation: 535

What a nice, clean answer, Tim. I needed a Python version, and this seems to cut it:

lines = """LINE 1.
LINE 2.
LINE 3.
LINE 4.
LINE 5.
LINE 6."""

import re
print(re.compile("(?:^.*$\n?){1,3}",re.M).findall(lines))

Gives the result

['LINE 1.\nLINE 2.\nLINE 3.\n', 'LINE 4.\nLINE 5.\nLINE 6.']

Subsituting with 4 instead of 3 should give

['LINE 1.\nLINE 2.\nLINE 3.\nLINE 4.\n', 'LINE 5.\nLINE 6.']

And indeed it does!

Upvotes: 0

Tim Pietzcker
Tim Pietzcker

Reputation: 336128

First, you don't want to use split() here because you would need a regex engine with full lookaround assertion support for that. Fortunately, .match() can do this just as well (arguably even better):

result = subject.match(/(?:^.*$\n?){1,3}/mg);

Test it live on regex101.com.

Explanation:

(?:    # Start a non-capturing group that matches...
 ^     # (from the start of a line)
 .*    # any number of non-newline characters
 $     # (until the end of the line).
 \n?   # Then it matches a newline character, if present.
){1,3} # It repeats this three times. If there are less than three lines
       # at the end of the string, it is content with matching two or one, as well.

Upvotes: 2

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