How do I trim whitespace?

Question

Is there a Python function that will trim whitespace (spaces and tabs) from a string?

"  \t example string\t  "   →   "example string"

Solution 1

For whitespace on both sides, use str.strip:

s = "  \t a string example\t  "
s = s.strip()

For whitespace on the right side, use str.rstrip:

s = s.rstrip()

For whitespace on the left side, use str.lstrip:

s = s.lstrip()

You can provide an argument to strip arbitrary characters to any of these functions, like this:

s = s.strip(' \t\n\r')

This will strip any space, \t, \n, or \r characters from both sides of the string.

The examples above only remove strings from the left-hand and right-hand sides of strings. If you want to also remove characters from the middle of a string, try re.sub:

import re
print(re.sub('[\s+]', '', s))

That should print out:

astringexample

Solution 2

In Python trim methods are named strip:

str.strip()  # trim
str.lstrip()  # left trim
str.rstrip()  # right trim

Solution 3

For leading and trailing whitespace:

s = '   foo    \t   '
print s.strip() # prints "foo"

Otherwise, a regular expression works:

import re
pat = re.compile(r'\s+')
s = '  \t  foo   \t   bar \t  '
print pat.sub('', s) # prints "foobar"

Solution 4

You can also use very simple, and basic function: str.replace(), works with the whitespaces and tabs:

>>> whitespaces = "   abcd ef gh ijkl       "
>>> tabs = "        abcde       fgh        ijkl"

>>> print whitespaces.replace(" ", "")
abcdefghijkl
>>> print tabs.replace(" ", "")
abcdefghijkl

Simple and easy.

Solution 5

#how to trim a multi line string or a file

s=""" line one
\tline two\t
line three """

#line1 starts with a space, #2 starts and ends with a tab, #3 ends with a space.

s1=s.splitlines()
print s1
[' line one', '\tline two\t', 'line three ']

print [i.strip() for i in s1]
['line one', 'line two', 'line three']




#more details:

#we could also have used a forloop from the begining:
for line in s.splitlines():
    line=line.strip()
    process(line)

#we could also be reading a file line by line.. e.g. my_file=open(filename), or with open(filename) as myfile:
for line in my_file:
    line=line.strip()
    process(line)

#moot point: note splitlines() removed the newline characters, we can keep them by passing True:
#although split() will then remove them anyway..
s2=s.splitlines(True)
print s2
[' line one\n', '\tline two\t\n', 'line three ']

View more solutions

Comments

[Chris]

Thanks for the heads up. I'd discovered the strip function earlier, but it doesn't seem to be working for my input..

[Sheep]

The characters python considers whitespace are stored in string.whitespace.

[user1066101]

By "strip function" do you mean strip method? " it doesn't seem to be working for my input" Please provide your code, your input and the output.

[demongolem]

For everything? How about equals ignore case? That is an unfortunate case where it is much easier in nearly every other language.

[vipin]

stackoverflow.com/questions/3739909/…

[Breno Baiardi]

Possible duplicate of Trimming a string in Python

[Evan Fosmark]

You didn't compile your regex. You need to make it be pat = re.compile(r'\s+')

[ton]

Results for the examples should be quite helpful :)

[jesuis]

No need to list the whitespace characters: docs.python.org/2/library/string.html#string.whitespace

[Jay Taylor]

As pointed by mh, you don't need to specify ' \t\n\r', as those will be stripped by default.

[user3467349]

You generally want to sub(" ", s) not "" the later will merge the words and you'll no longer be able to use .split(" ") to tokenize.

[imrek]

None of the above seem to strip all white spaces in some cases. I still have tones of tabs in the middle of a string.

[James Thompson]

@Drunken Master - Sorry for not being more clear, the examples above are only for left-hand, right-hand and both sides of a string. I've added another example that shows how to remove whitespace from the middle of a string.

[Ron Klein]

it would be nice to see the output of the print statements

[Smoke Liberator]

The regex in the final example should be [\s]+. Tagging the string as a raw in a regex is something I typically do, so print re.sub(r'[\s]+','',s). More about raw strings and escaping here: stackoverflow.com/questions/2241600/python-regex-r-prefix

[Jorge E. Cardona]

The last example is exactly as using str.replace(" ",""). You don't need to use re, unless you have more than one space, then your example doesn't work. [] is designed to mark single characters, it's unnecessary if you're using just \s. Use either \s+ or [\s]+ (unnecessary) but [\s+] doesn't do the job, in particular if you want to replace the multiple spaces with a single one like turning "this example" into "this example".

[Le Droid]

Simple and efficient. Could use " ".join(... to keep words separated with a space.

[ArtOfWarfare]

@JorgeE.Cardona - One thing you're slightly wrong about - \s will include tabs while replace(" ", "") won't.

[Matt Fletcher]

One of those fun things about coming from JS to Python is trying to remember differences like this! Strip, not trim. Strip, not trim.

[yantrab]

Why use a regex when s.strip() does exactly this?

[Rafe]

s.strip() only handles the initial white space, but not whitespace "discovered" after removing other unwanted characters. Note that this will remove even the whitespace after the final leading \n

[Rafe]

Someone down-voted this answer but didn't explain why it is flawed. Shame on you (@NedBatchelder if the down vote was you please reverse as I explained your question and you didn't mention anything actually broken with my answer)

[yantrab]

Rafe, you might want to double-check: s.strip() produces precisely the same result as your regex.

[iMitwe]

@Rafe, you're confusing it with trim. Strip does the required operations.

[Brandon Rhodes]

But this, alas, also removes interior space, while the example in the original question leaves interior spaces untouched.

[Rafe]

Wow you are right, thanks for pointing that out. I'd like to delete this answer if possible (is grayed out so maybe already done?)

[isar]

which is easy to remember because strip looks almost like trim.