[Python-3000] More wishful thinking

[Talin]

Talin <talin <at> acm.org> writes:

> 2) A suggestion which I've seen others bring up before is the use of
> the * operator for tuple packing / unpacking operations, i.e.:
> 
>     a, *b = (1, 2, 3)

I wanted to add another case that I run across in my code a lot.

I often times want to split off a single leading word or token
from a string, but I don't know in advance whether or not the
split will actually succeed.

For example, suppose you want to render the first word of
a paragraph in a different style:

   first, rest = paragraph.split( ' ', 1 )

Unfortunately, if the paragraph only contains a single word,
this blows up. So what you end up having to do is:

   parts = paragraph.split( ' ', 1 )
   if len( parts ) > 1:
      first, rest = parts
   else:
      first = parts[ 0 ]
      rest = ""

My objection here is that the intent of the code is cluttered
up by the error-handling logic.

If I could do an argument-style unpack, however, I could instead
write:

   first, *rest = paragraph.split( ' ', 1 )

It does mean that 'rest' is wrapped in a tuple, but that's not a
terrible hardship. If there's no second word, then 'rest' is an
empty tuple, which is easy to test with "if rest" and such.

-- Talin