Add list to set?

Question

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 1

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.