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Mueen Nawaz <m.n### [at] ieee org> wrote:
> nemesis wrote:
> > It can take arbitrary objects as keys and has a wealth of good methods to choose
> > from. Perhaps it's time for some friday night troll? ;)
>
> Unless they made changes, that's not correct. It can only take strings,
> numbers, and immutable types as keys (so no lists, but yes tuples).
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> ls = dir()
>>> ls
['__builtins__', '__doc__', '__name__']
>>> d = {}
>>> d[ls]=1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: list objects are unhashable
>>> str
<type 'str'>
>>> d[str]="string class"
>>> d
{<type 'str'>: 'string class'}
>>> d[lambda x:x+1]="function object as key"
>>> d
{<type 'str'>: 'string class', <function <lambda> at 0x838aa3c>: 'function
object as key'}
True, lists can't be used as key. But classes, objects and even functions can.
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