[Tutor] TypeError: unhashable type: 'pygame.math.Vector2'

[Mats Wichmann]

On 6/26/20 8:25 AM, Cravan wrote:
> Sadly, an error pops up when I change the code.
> Here's my edited code for the class file:

> However, this error pops up:
> #######
> Traceback (most recent call last):
>   File "maze.py", line 181, in <module>
>     g.run()
>   File "maze.py", line 53, in run
>     self.update()
>   File "maze.py", line 109, in update
>     action_ = maxAction(Q, observationnew, possible_actions)
>   File "maze.py", line 177, in maxAction
>     values = np.array([Q[state,a] for a in actions])
>   File "maze.py", line 177, in <listcomp>
>     values = np.array([Q[state,a] for a in actions])
> KeyError: ((6, 26), 'U')
> ######
> 
> Apologies for the (late) and long email here, would appreciate if someone could offer some help.
Well, again the error tells you what is happening: KeyError means you
tried to look up a key in a dictionary that is actually not present in
the dictionary.

So Q does not contain the tuple  ((6, 26), 'U')

only you can tell if that's a legitimate result, or an unexpected one.

if it's *expected* that there will be some mismatches, you can do this:

try:
    values = np.array([Q[state,a] for a in actions])
except KeyError:
    # take appropriate action for missing key

If it's unexpected, then you have some recoding to do.