string - How to remove empty lines with or without whitespace in Python

Question

I have large string which I split by newlines. How can I remove all lines that are empty, (whitespace only)?

pseudo code:

for stuff in largestring:
   remove stuff that is blank

Answer 1

Using regex:

if re.match(r'^\s*$', line):
    # line is empty (has only the following: \t\n\r and whitespace)

Using regex + filter():

filtered = filter(lambda x: not re.match(r'^\s*$', x), original)

As seen on codepad.

Answer 2

Try list comprehension and string.strip():

>>> mystr = "L1\nL2\n\nL3\nL4\n  \n\nL5"
>>> mystr.split('\n')
['L1', 'L2', '', 'L3', 'L4', '  ', '', 'L5']
>>> [line for line in mystr.split('\n') if line.strip() != '']
['L1', 'L2', 'L3', 'L4', 'L5']

Answer 3

I also tried regexp and list solutions, and list one is faster.

Here is my solution (by previous answers):

text = "\n".join([ll.rstrip() for ll in original_text.splitlines() if ll.strip()])

Answer 4

lines = bigstring.split('\n')
lines = [line for line in lines if line.strip()]

Answer 5

Surprised a multiline re.sub has not been suggested (Oh, because you've already split your string... But why?):

>>> import re
>>> a = "Foo\n \nBar\nBaz\n\n   Garply\n  \n"
>>> print a
Foo

Bar
Baz

        Garply


>>> print(re.sub(r'\n\s*\n','\n',a,re.MULTILINE))
Foo
Bar
Baz
        Garply

>>> 

Answer 6

If you are not willing to try regex (which you should), you can use this:

s.replace('\n\n','\n')

Repeat this several times to make sure there is no blank line left. Or chaining the commands:

s.replace('\n\n','\n').replace('\n\n','\n')

_{Just to encourage you to use regex, here are two introductory videos that I find intuitive:
• Regular Expressions (Regex) Tutorial
• Python Tutorial: re Module}

Answer 7

you can simply use rstrip:

    for stuff in largestring:
        print(stuff.rstrip("\n")

Answer 8

I use this solution to delete empty lines and join everything together as one line:

match_p = re.sub(r'\s{2}', '', my_txt) # my_txt is text above

Answer 9

My version:

while '' in all_lines:
    all_lines.pop(all_lines.index(''))

Answer 10

Use positive lookbehind regex:

re.sub(r'(?<=\n)\s+', '', s, re.MULTILINE)

When you input:

foo
<tab> <tab>

bar

The output will be:

foo
bar

Answer 11

Same as what @NullUserException said, this is how I write it:

removedWhitespce = re.sub(r'^\s*$', '', line)