Remove all whitespace in a string

To remove only spaces use str.replace:

sentence = sentence.replace(' ', '')

To remove all whitespace characters (space, tab, newline, and so on) you can use split then join:

sentence = ''.join(sentence.split())

or a regular expression:

import re
pattern = re.compile(r'\s+')
sentence = re.sub(pattern, '', sentence)

If you want to only remove whitespace from the beginning and end you can use strip:

sentence = sentence.strip()

You can also use lstrip to remove whitespace only from the beginning of the string, and rstrip to remove whitespace from the end of the string.

An alternative is to use regular expressions and match these strange white-space characters too. Here are some examples:

Remove ALL whitespace in a string, even between words:

import re
sentence = re.sub(r"\s+", "", sentence, flags=re.UNICODE)

Remove whitespace in the BEGINNING of a string:

import re
sentence = re.sub(r"^\s+", "", sentence, flags=re.UNICODE)

Remove whitespace in the END of a string:

import re
sentence = re.sub(r"\s+$", "", sentence, flags=re.UNICODE)

Remove whitespace both at the BEGINNING and at the END of a string:

import re
sentence = re.sub("^\s+|\s+$", "", sentence, flags=re.UNICODE)

Remove ONLY DUPLICATE whitespace:

import re
sentence = " ".join(re.split("\s+", sentence, flags=re.UNICODE))

(All examples work in both Python 2 and Python 3)

"Whitespace" includes space, tabs, and CRLF. So an elegant and one-liner string function we can use is str.translate:

Python 3

' hello  apple '.translate(str.maketrans('', '', ' \n\t\r'))

OR if you want to be thorough:

import string
' hello  apple'.translate(str.maketrans('', '', string.whitespace))

Python 2

' hello  apple'.translate(None, ' \n\t\r')

OR if you want to be thorough:

import string
' hello  apple'.translate(None, string.whitespace)

For removing whitespace from beginning and end, use strip.

>> "  foo bar   ".strip()
"foo bar"

' hello  \n\tapple'.translate({ord(c):None for c in ' \n\t\r'})

MaK already pointed out the "translate" method above. And this variation works with Python 3 (see this Q&A).

In addition, strip has some variations:

Remove spaces in the BEGINNING and END of a string:

sentence= sentence.strip()

Remove spaces in the BEGINNING of a string:

sentence = sentence.lstrip()

Remove spaces in the END of a string:

sentence= sentence.rstrip()

All three string functions strip lstrip, and rstrip can take parameters of the string to strip, with the default being all white space. This can be helpful when you are working with something particular, for example, you could remove only spaces but not newlines:

" 1. Step 1\n".strip(" ")

Or you could remove extra commas when reading in a string list:

"1,2,3,".strip(",")

Be careful:

strip does a rstrip and lstrip (removes leading and trailing spaces, tabs, returns and form feeds, but it does not remove them in the middle of the string).

If you only replace spaces and tabs you can end up with hidden CRLFs that appear to match what you are looking for, but are not the same.

eliminate all the whitespace from a string, on both ends, and in between words.

>>> import re
>>> re.sub("\s+", # one or more repetition of whitespace
    '', # replace with empty string (->remove)
    ''' hello
...    apple
... ''')
'helloapple'

• https://en.wikipedia.org/wiki/Whitespace_character

Python docs:

• https://docs.python.org/library/stdtypes.html#textseq
• https://docs.python.org/library/stdtypes.html#str.replace
• https://docs.python.org/library/string.html#string.replace
• https://docs.python.org/library/re.html#re.sub
• https://docs.python.org/library/re.html#regular-expression-syntax

I use split() to ignore all whitespaces and use join() to concatenate strings.

sentence = ''.join(' hello  apple  '.split())
print(sentence) #=> 'helloapple'

I prefer this approach because it is only a expression (not a statement).
It is easy to use and it can use without binding to a variable.

print(''.join(' hello  apple  '.split())) # no need to binding to a variable

import re    
sentence = ' hello  apple'
re.sub(' ','',sentence) #helloworld (remove all spaces)
re.sub('  ',' ',sentence) #hello world (remove double spaces)

In the following script we import the regular expression module which we use to substitute one space or more with a single space. This ensures that the inner extra spaces are removed. Then we use strip() function to remove leading and trailing spaces.

# Import regular expression module
import re

# Initialize string
a = "     foo      bar   "

# First replace any number of spaces with a single space
a = re.sub(' +', ' ', a)

# Then strip any leading and trailing spaces.
a = a.strip()

# Show results
print(a)

All string characters are unicode literal in Python 3; as a consequence, since str.split() splits on all white space characters, that means it splits on unicode white space characters. So split + join syntax (as in 1, 2, 3) will produce the same output as re.sub with the UNICODE flag (as in 4); in fact, the UNICODE flag is redundant here (as in 2, 5, 6, 7).

import re
import sys

# all unicode characters
sentence = ''.join(map(chr, range(sys.maxunicode+1)))

# remove all white space characters
x = ''.join(sentence.split())
y = re.sub(r"\s+", "", sentence, flags=re.UNICODE)
z = re.sub(r"\s+", "", sentence)

x == y == z      # True

In terms of performance, since Python's string methods are optimized, they are much faster than regex. As the following timeit test shows, when removing all white space characters from the string in the OP, Python string methods are over 7 times faster than re option.

import timeit

import timeit

setup = """
import re
s = ' hello  \t apple  '
"""

t1 = min(timeit.repeat("''.join(s.split())", setup))
t2 = min(timeit.repeat("re.sub(r'\s+', '', s, flags=re.UNICODE)", setup))


t2 / t1  # 7.868004799367726

I found that this works the best for me:

test_string = '  test   a   s   test '
string_list = [s.strip() for s in str(test_string).split()]
final_string = ' '.join(string_array)
# final_string: 'test a s test'

It removes any whitespaces, tabs, etc.

Just addition to the Emil Stenström's answer

This code removes all white spaces and you could also remove your own extra utf-8 characters.

import re

def utf8trim(s: str) -> str:
    spaces = "|".join([r"\s", "\u2800", "\u3164", "\u1160", "\uFFA0", "\u202c"])
    return re.sub(f"^[{spaces}]+|[{spaces}]+$", "", s, flags=re.UNICODE)

try this.. instead of using re i think using split with strip is much better

def my_handle(self):
    sentence = ' hello  apple  '
    ' '.join(x.strip() for x in sentence.split())
#hello apple
    ''.join(x.strip() for x in sentence.split())
#helloapple