[Tutor] Unexpected iterator

[Kent Johnson]

On Mon, Nov 16, 2009 at 12:17 AM, spir <denis.spir at free.fr> wrote:
> Le Sun, 15 Nov 2009 19:23:33 -0000,
> "Alan Gauld" <alan.gauld at btinternet.com> s'exprima ainsi:
>
>> What does 'unpack' mean?  I've seen a few Python errors about packing
>> and unpacking.  What does it mean?
>
> Unpacking is rarely needed. It matches some kind of problems.

Not needed, I suppose, since there is another way to write the code,
but using tuple unpacking can greatly reduce the length and improve
the readability of your code.

> Imagine you parse "codes" each made of name-sep-number. Then when walking through the result you can write:
> for code in codes:
>        (name,sep,number) = code

Or even
  for name, sep, number in codes:
    # Do something with name, sep, number

> It's just an elegant manner to avoid indexing -- right?

It avoids indexing and gives meaningful names to values. Compare the
above with the alternatives:
  for code in codes:
    name = code[0]
    sep = code[1]
    number = code[2]
    # Do something with name, sep, number

or

  for code in codes:
    # Do something with code[0], code[1], code[2]

The first alternative is much more verbose while the second one is
much harder to understand.

Kent