[Python-Dev] string slicing and method consistency

[Greg Wilson]

One of the students in my class at the Space Telescope
Science Institute ("Hubble R Us") last week brought up
an interesting point: if "abbc"[-1] is "c", and if
"abbc".replace("b", "x", 1) is "axbc", then shouldn't
"abbc".replace("b", "x", -1) be "abxc" (i.e. negative
numbers replace the *last* occurrences of the value)?
Same argument for "split", etc.

Turns out that "abbc".replace("b", "x", -1) is "axxc"
(i.e. negative arguments are ignored).  I would have
expected this to raise a ValueError, if anything.  Is
there a reason for this behavior?  Is it worth making
replace, split, etc. interpret negative indices in the
same way as indexing does?

Thanks,
Greg