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A ReversibleList behaves like a normal list when ReversibleList.reversed == False, but it behaves as if it had been reversed when ReversibleList.reversed == True. The trick is that the underlying list is never actually reversed. This can be a boon for performance [citation needed] if whatever one's doing requires reversing and unreversing a particular list many times, or reversing many lists.

UPDATE: Thanks everyone for the suggestions! I made a follow up version here which fixes the bugs, incorporates the feedback, and has more tests.

A ReversibleList behaves like a normal list when ReversibleList.reversed == False, but it behaves as if it had been reversed when ReversibleList.reversed == True. The trick is that the underlying list is never actually reversed. This can be a boon for performance [citation needed] if whatever one's doing requires reversing and unreversing a particular list many times, or reversing many lists.

A ReversibleList behaves like a normal list when ReversibleList.REVERSED == False, but it behaves as if it had been reversed when ReversibleList.REVERSED == True. The trick is that the underlying list is never actually reversed. This can be a boon for performance [citation needed] if whatever one's doing requires reversing and unreversing a particular list many times, or reversing many lists.

A ReversibleList behaves like a normal list when ReversibleList.reversed == False, but it behaves as if it had been reversed when ReversibleList.reversed == True. The trick is that the underlying list is never actually reversed. This can be a boon for performance [citation needed] if whatever one's doing requires reversing and unreversing a particular list many times, or reversing many lists.

a = ReversibleList([0, 1, 2, 3, 4, 5])
print(a[1]) # 1
print(a) # [0, 1, 2, 3, 4, 5]
print(a[:]) # [0, 1, 2, 3, 4, 5]
print(repr(a)) # ReversibleList([0, 1, 2, 3, 4, 5])

a.reverse()
print(a[1]) # 4
print(a) # [5, 4, 3, 2, 1, 0]
print(a[:]) # [5, 4, 3, 2, 1, 0]
print(repr(a)) # ReversibleList([0, 1, 2, 3, 4, 5])

a[:] = a
print(a) # [5, 4, 3, 2, 1, 0]

a[2:5] = a[2:5]
print(a) # [5, 4, 3, 2, 1, 0]

print(a[2:5]) # [3, 2, 1]

a[2:5] = [3, 2, 1]
print(a) # [5, 4, 3, 2, 1, 0]

a[2:5] = ReversibleList([1, 2, 3])
print(a) # [5, 4, 3, 2, 1, 0]
```

a = ReversibleList([0, 1, 2, 3, 4, 5])
print(a[1]) # 1
print(a) # [0, 1, 2, 3, 4, 5]
print(a[:]) # [0, 1, 2, 3, 4, 5]
print(repr(a)) # ReversibleList([0, 1, 2, 3, 4, 5])

a.reverse()
print(a[1]) # 4
print(a) # [5, 4, 3, 2, 1, 0]
print(a[:]) # [5, 4, 3, 2, 1, 0]
print(repr(a)) # ReversibleList([0, 1, 2, 3, 4, 5])

a[:] = a
print(a) # [5, 4, 3, 2, 1, 0]

a[2:5] = a[2:5]
print(a) # [5, 4, 3, 2, 1, 0]

print(a[2:5]) # [3, 2, 1]

a[2:5] = [3, 2, 1]
print(a) # [5, 4, 3, 2, 1, 0]

a[2:5] = ReversibleList([1, 2, 3])
print(a) # [5, 4, 3, 2, 1, 0]