Addition to slice syntax (for strings)

[Skip Montanaro]

>>>>> "Will" == Will McGugan <news at NOwillmcguganSPAM.com> writes:

    Will> I'd like to suggest an addition to the slice syntax. How about
    Will> allowing strings as arguments to slices on strings, and interpret
    Will> them as the index of the substring found within the string being
    Will> sliced. I'm sure I didnt explain that too well, so here is an
    Will> example..

How would you interpret

    >>> s = "my dog has fleas"
    >>> s['x':'z']              # both strings nonexistent
    >>> s['z':'f']              # first string nonexistent
    >>> s['f':'z']              # second string nonexistent
    >>> s['g':'d']              # second appears earlier than first

Returning the empty string in all cases is plausible, but other
possibilities make sense at some level:

    s['x':'z'] => ""
    s['x':'z'] => "my dog has fleas"
    s['z':'f'] => "my dog has f"
    s['z':'f'] => "my dog has "
    s['f':'z'] => "leas"
    s['f':'z'] => "fleas"
    s['g':'d'] => ""
    s['g':'d'] => "god"

Two other quibbles about your example:

    * why not use s.rfind("...") instead of s.find("...") for the second
      index?

    * why add 1 to the offset of the second index?

In short, there is enough uncertainty in what the "right" thing to do is, I
suspect you'd be better off just subclassing strings when you need this sort
of functionality in your apps.

Skip