[Python-ideas] New explicit methods to trim strings

[Stephen J. Turnbull]

MRAB writes:
 > On 2019-04-02 19:10, Stephen J. Turnbull wrote:

 > >      word[len(prefix) if word.startswith(prefix) else 0:]

 > It could be 'improved' more to:
 > 
 >      word[word.startswith(prefix) and len(prefix) : ]

Except that it would be asymmetric with suffix.  That probably doesn't
matter given the sequence[:-0] bug.

BTW thank you for pointing out that bug (and not quoting the code
where I deliberately explicitly introduced the null suffix! ;-)  This
works:

    word[:-len(suffix) or len(word)] if word.endswith(suffix) else word

Do tutorials mention this pitfall with computed indicies (that -0 is
treated as "beginning of sequence")?  (I should check myself, but
can't spend time this week and so probably won't. :-( )

 > > prefix.  So that's the one I'd go with, as I can't think of any
 > > applications where multiple copies of the same string would be useful.

 > _Neither_ version copies if the word doesn't start with the prefix. If 
 > you won't believe me, test them! :-)

Oh, I believe you.  It just means somebody long ago thought more
deeply about the need for copying immutable objects than I ever have.