Tuple __eq__ fails when spaces aren't of the same type

[lebrice]

When creating a gym.spaces.Tuple, if a list of spaces is passed as the spaces argument, I believe it should be converted to a tuple, as otherwise the space could be modified, which doesn't seem like an intended behaviour, and comparisons with other equivalent spaces.Tuple objects, but created with tuple arguments, will fail:

inner_spaces = [
        Box(0, 1, (2,2)),
        Discrete(2),
        Box(0, 1, (2,2)),
]
space_1 = spaces.Tuple(list(inner_spaces))
space_2 = spaces.Tuple(tuple(inner_spaces))
assert space_1 == space_2 # This fails
assert space_2 == space_1 # This also

The way I see it, this can be easily fixed in one of two ways:

1. Convert the spaces argument to a tuple in the constructor:

   def __init__(self, spaces):
       self.spaces = tuple(spaces)
       for space in spaces:
           assert isinstance(space, Space), "Elements of the tuple must be instances of gym.Space"
       super(Tuple, self).__init__(None, None)

   However this might change the behaviour of some programs which depend on being able to modify Tuple spaces.

2. Convert the spaces argument to a tuple just when comparing:

   def __eq__(self, other):
       return isinstance(other, Tuple) and tuple(self.spaces) == tuple(other.spaces)

   This won't copy anything if self.spaces is already a tuple, however for lists its a small copy.

Let me know what you think!

[Yuchen0604]

Hi, I also use spaces.Tuple as my observation space, which algorithm do you use? I want to use dqn, and it seems that dqn requires env.ovservation_space.shape, but Tuple doesn't have the shape method. I was wondering, how do you combine Tuple with your algorithm? thanks in advance!

[jkterry1]

@lebrice should this issue still be open?

[lebrice]

Hey @jkterry1 I'll check if it's still reproducible and I'll get back to you.