Strange Python strip() behavior

Question

I don't understand why the strip() function returns the way it does below. I want to strip() the last occurence of Axyx. I got around it by using rstrip('Axyx') but what's the explanation for the following?

>>>"Abcd Efgh Axyx".strip('Axyx')
'bcd Efgh '

Ismail Badawi · Accepted Answer · 2015-10-24T19:07:31.110

4

The string passed to strip is treated as a bunch of characters, not a string. Thus, strip('Axyx') means "strip occurrences of A, x, or y from either end of the string".

If you actually want to strip a prefix or suffix, you'd have to write that logic yourself. For example:

s = 'Abcd Efgh Axyx'
if s.endswith('Axyx'):
    s = s[:-len('Axyx')]

edited Oct 24 '15 at 19:07

answered Oct 24 '15 at 19:03

Ismail Badawi

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Is there a compact way to delete the first occurence of a substring from the right from a string? – user2399453 Oct 24 '15 at 19:05
Is the 'Axyx' that you want to delete always at the very end of the string, or is there sometimes material in between 'Axyx' and the end? – user2034412 Oct 24 '15 at 19:07
From re module Use re.sub() – Ahsanul Haque Oct 24 '15 at 19:07
Its always at the end but there might be a space after it – user2399453 Oct 24 '15 at 19:07
@user3079275 See edit – Ismail Badawi Oct 24 '15 at 19:08
The answer here works if you also check for the space. An alternative is to use `re.sub()` to substitute a string for a regular expression match. If your string is `s`, then you'd do: `s = re.sub('Axyx ?$', '', s)` – user2034412 Oct 24 '15 at 19:10
I had to do x = x[:-(1+len('Axyx'))].strip() and it works. Its len() + 1 – user2399453 Oct 24 '15 at 19:16

score 0 · Answer 2 · answered Oct 24 '15 at 19:05

Because strip() returns a copy of the string that you provided without the characters that you gave as input.
For example: "12345".strip('123') returns: '45'.
So, strip() does not remove words or something but removes all the characters that the string that you give as input has, both from the end and the beginning of the string that you want to strip.

Strange Python strip() behavior

2 Answers2