You are creating a set via set(...) call, and set needs hashable items. You can’t have set of lists. Because list’s arent hashable.
[[(a,b) for a in range(3)] for b in range(3)] is a list. It’s not a hashable type. The __hash__ you saw in dir(…) isn’t a method, it’s just None.
A list comprehension returns a list, you don’t need to explicitly use list there, just use:
>>> [[(a,b) for a in range(3)] for b in range(3)]
[[(0, 0), (1, 0), (2, 0)], [(0, 1), (1, 1), (2, 1)], [(0, 2), (1, 2), (2, 2)]]
Try those:
>>> a = {1, 2, 3}
>>> b= [1, 2, 3]
>>> type(a)
<class 'set'>
>>> type(b)
<class 'list'>
>>> {1, 2, []}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> print([].__hash__)
None
>>> [[],[],[]] #list of lists
[[], [], []]
>>> {[], [], []} #set of lists
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'