Tested on Python 2.6 interpreter:
>>> a=set('abcde')
>>> a
set(['a', 'c', 'b', 'e', 'd'])
>>> l=['f','g']
>>> l
['f', 'g']
>>> a.add(l)
Traceback (most recent call last):
File "<pyshell#35>", line 1, in <module>
a.add(l)
TypeError: list objects are unhashable
I think that I can't add the list to the set because there's no way Python can tell If I have added the same list twice. Is there a workaround?
EDIT: I want to add the list itself, not its elements.
Answer
Use set.update() or |=
>>> a = set('abc')
>>> l = ['d', 'e']
>>> a.update(l)
>>> a
{'e', 'b', 'c', 'd', 'a'}
>>> l = ['f', 'g']
>>> a |= set(l)
>>> a
{'e', 'b', 'f', 'c', 'd', 'g', 'a'}
edit: If you want to add the list itself and not its members, then you must use a tuple, unfortunately. Set members must be hashable.