What's a quick one-liner to remove empty lines from a python string?

Question

I have some code in a python string that contains extraneous empty lines. I would like to remove all empty lines from the string. What's the most pythonic way to do this?

Note: I'm not looking for a general code re-formatter, just a quick one or two-liner.

Thanks!

Answer 1

How about:

text = os.linesep.join([s for s in text.splitlines() if s])

where text is the string with the possible extraneous lines?

Answer 2

"\n".join([s for s in code.split("\n") if s])

Edit2:

text = "".join([s for s in code.splitlines(True) if s.strip("\r\n")])

I think that's my final version. It should work well even with code mixing line endings. I don't think that line with spaces should be considered empty, but if so then simple s.strip() will do instead.

Answer 3

This one will remove lines of spaces too.

re.replace(u'(?imu)^\s*\n', u'', code)

Answer 4

Suprised there's no love for the standard string replace method. But maybe it doesn't qualify as a one-liner, since it's just a plain old method call.

>>> manylines = 'hello\nworld\n!'
>>> print manylines
hello
world
!

>>> no_linefeeds = manylines.replace('\n', '')
>>> print no_linefeeds
helloworld!

Answer 5

filter(None, code.splitlines())
filter(str.strip, code.splitlines())

are equivalent to

[s for s in code.splitlines() if s]
[s for s in code.splitlines() if s.strip()]

and might be useful for readability

Answer 6

And now for something completely different:

Python 1.5.2 (#0, Apr 13 1999, 10:51:12) [MSC 32 bit (Intel)] on win32
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> import string, re
>>> tidy = lambda s: string.join(filter(string.strip, re.split(r'[\r\n]+', s)), '\n')
>>> tidy('\r\n   \n\ra\n\n   b   \r\rc\n\n')
'a\012   b   \012c'

Episode 2:

This one doesn't work on 1.5 :-(

BUT not only does it handle universal newlines and blank lines, it also removes trailing whitespace (good idea when tidying up code lines IMHO) AND does a repair job if the last meaningful line is not terminated.

import re
tidy = lambda c: re.sub(
    r'(^\s*[\r\n]+|^\s*\Z)|(\s*\Z|\s*[\r\n]+)',
    lambda m: '\n' if m.lastindex == 2 else '',
    c)