python: rstrip one exact string, respecting order

Question

Is it possible to use the python command rstrip so that it does only remove one exact string and does not take all letters separately?

I was confused when this happened:

>>>"Boat.txt".rstrip(".txt")
>>>'Boa'

What I expected was:

>>>"Boat.txt".rstrip(".txt")
>>>'Boat'

Can I somehow use rstrip and respect the order, so that I get the second outcome?

`rstrip` is the wrong method because it will look at `".txt"`, and understand it as something like `['.', 't', 'x', 't']` aka "keep removing characters that matches those in that list until you reach a character that is not in that list. — neverendingqs, Jul 22 '15 at 15:06

falsetru · Accepted Answer · 2013-09-10T15:59:59.470

60

You're using wrong method. Use str.replace instead:

>>> "Boat.txt".replace(".txt", "")
'Boat'

NOTE: str.replace will replace anywhere in the string.

>>> "Boat.txt.txt".replace(".txt", "")
'Boat'

To remove the last trailing .txt only, you can use regular expression:

>>> import re
>>> re.sub(r"\.txt$", "", "Boat.txt.txt")
'Boat.txt'

If you want filename without extension, os.path.splitext is more appropriate:

>>> os.path.splitext("Boat.txt")
('Boat', '.txt')

edited Sep 10 '13 at 15:59

answered Sep 10 '13 at 15:54

falsetru

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3

Note that this will replace anywhere in the string. – Amber Sep 10 '13 at 15:55
@Amber, Thank you for comment. I mention that. – falsetru Sep 10 '13 at 15:57
5

Note, regex is an overkill here. `os.path.splitext` would only work if the pattern of the separator matches an extension. @nneonneo 's solution fits all cases. – Abhijit Sep 10 '13 at 16:09
@Amber what if `count` is defined? Then only the first occured instance is replaced, right? – MJimitater Mar 16 '21 at 14:32

score 41 · Answer 2 · edited Feb 23 '21 at 14:57

41

Starting with Python 3.9, use .removesuffix():

"Boat.txt".removesuffix(".txt")

On earlier versions of Python, you'll have to either define it yourself:

def removesuffix(s, suf):
    if suf and s.endswith(suf):
        return s[:-len(suf)]
    return s

(you need to check that suf isn't empty, otherwise removing an empty suffix e.g. removesuffix("boat", "") will do return s[:0] and return "" instead of "boat")

or use regex:

import re
suffix = ".txt"
s = re.sub(re.escape(suffix) + '$', '', s)

edited Feb 23 '21 at 14:57

Boris Verkhovskiy

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answered Sep 10 '13 at 15:58

nneonneo

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2

This `strip_suffix(s, suf)` solution is the best answer here, as the accepted solution with `.replace()` is replacing one slightly dangerous solution to the with another slightly dangerous solution. Both the original `.rstrip` and `.replace` are liable to occasionally return results contrary to the original intent of the OP. I wonder why Python does not have something like this built in.. – cardamom Apr 01 '19 at 12:32
Minor improvment: `len(s)` can be dropped, a negative offset is sufficient. – guidot Aug 12 '20 at 15:32
1

If you look at the edit history, I originally used only a negative offset. However, it was edited by @wim to include len(s) in order to make it work in the case where the suffix is empty. I agree with this change - it would subtly truncate the entire string with an empty suffix which would be quite unexpected behaviour (even if an empty suffix isn’t something you’d usually use). – nneonneo Aug 12 '20 at 15:55
@guidot Actually, if you remove `len(s)` in the splicing (i.e. `return s[:-len(suf)]`), passing an empty suffix (`suf=''`) will result in an empty return value! You would have to check that the suffix is not empty (i.e. `if suf and s.endswith(suf)`). – TedGrassman Nov 05 '20 at 14:39
Woops, @nneonneo already addressed the empty suffix case ^^ Anyway, it's worth pointing out because I too thought I was optimizing the function by removing `len(s)` and using a negative offset, only to encounter a bug much later due to empty suffix resulting in a empty return string! – TedGrassman Nov 05 '20 at 14:53

score 13 · Answer 3 · edited Nov 19 '20 at 06:53

13

In Python 3.9, as part of PEP-616, you can now use the removeprefix and removesuffix functions:

>>> "Boat.txt".removeprefix("Boat")
>>> '.txt'

>>> "Boat.txt".removesuffix(".txt")
>>> 'Boat'

edited Nov 19 '20 at 06:53

Pikamander2

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answered Aug 12 '20 at 16:02

nneonneo

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score 1 · Answer 4 · answered Mar 14 '23 at 09:30

1

>>> foo="Boat.txt"
>>> foo[:foo.rfind(".txt")]
'Boat'

answered Mar 14 '23 at 09:30

Stanley Yang

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Th3carpenter · Answer 5 · 2015-02-02T13:58:46.337

>>> myfile = "file.txt"
>>> t = ""
>>> for i in myfile:
...     if i != ".":
...             t+=i
...     else:
...             break
... 
>>> t
'file'
>>> # Or You can do this
>>> import collections
>>> d = collections.deque("file.txt")
>>> while True:
...     try:
...             if "." in t:
...                     break
...             t+=d.popleft()
...     except IndexError:
...             break
...     finally:
...             filename = t[:-1]
... 
>>> filename
'file'
>>>

score 0 · Answer 6 · answered May 09 '18 at 14:31

This will work regardless of extension type.

# Find the rightmost period character
filename = "my file 1234.txt"

file_extension_position = filename.rindex(".")

# Substring the filename from first char up until the final period position
stripped_filename = filename[0:file_extension_position]
print("Stripped Filename: {}".format(stripped_filename))

score 0 · Answer 7 · answered Aug 18 '20 at 14:09

0

In addition to the other excellent answers, sometimes rpartiton may also get you there (depends on the exact usecase).

>> "Boat.txt".rpartition('.txt')
('Boat', '.txt', '')

>> "Boat.txt".rpartition('.txt')[0]
'Boat'

answered Aug 18 '20 at 14:09

Xaser

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python: rstrip one exact string, respecting order

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