Tuples, like other immutable data types, are hashable (assuming the contents are immutable as well), and so they can be used as keys to dictionaries.  Lists cannot be used this way.

>>> {['a']: 'a'}
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: list objects are unhashable
>>> {('a',): 'a'}
{('a',): 'a'}
>>>

  -Arcege

On 9/14/06, Tim Johnson <[EMAIL PROTECTED]> wrote:
* Kermit Rose <[EMAIL PROTECTED]> [060914 18:29]:
> Hello Brian.
>
> Today I read through chapter five of the python tutorial and discovered
> that tuples are not the same thing as lists.
>
> This surprised me.
>
> I do not see any difference in the capability of lists and tuples.

  Hi Kermit:

  Tuples are "read-only" - you can't modify a tuple,

  you can produce a tuple from a list by using the
  tuple() function.
  you can produce a list from a tuple by using the
  list() function - but the original tuple is unchanged.

  You can return multiple values from a function
  using tuples.
>
> Why would you use one in preference to the other?

  I use tuples as above and where I don't want data
  changed...

  tim
--
Tim Johnson <[EMAIL PROTECTED] >
      http://www.alaska-internet-solutions.com
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