[Tutor] tuples versus lists

[Michael P. Reilly]

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 <tim at johnsons-web.com> wrote:
>
> * Kermit Rose <kermit at polaris.net> [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 <tim at johnsons-web.com>
>       http://www.alaska-internet-solutions.com
> _______________________________________________
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>



-- 
There's so many different worlds,
So many different suns.
And we have just one world,
But we live in different ones.
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