Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> text = 'test1/1.jp2'
>>> text.rstrip('.jp2')
'test1/1'
>>> text = 'test1.jp2'
>>> text.rstrip('.jp2')
'test1'
>>> text = 'test1/2.jp2'
>>> text.rstrip('.jp2')
'test1/'
>>> 

Why the rstrip function stripped '2' from the last example? I think that it is a bug.

I think you misunderstand rstrip -- it works from the right, and checks to see if the right-most character is in the string you have given it.  As long as it is, then it will remove the character and loop

Example

>>> text = 'test1/1.jp2'
>>> text.rstrip('.2jp')
'test1/1'

Ok, thank you. I thought it trims whole sequence or nothing.

The 3.5 documentation of str.strip() was recently modified in Issue 24204 due to this kind of misunderstanding. Perhaps other versions should be modified as well, or the str.l/rstrip() methods, or the bytes() and bytearray() methods. See also Issue 23560 proposing to group the documentation of these methods together.