Yeah, I know. ^_^

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"I like it better than Python's "you can only store hashable things in keys" approach."

Well... you can only use hashable things as keys in Racket too. (How else would hash tables work?) Almost everything in Racket is hashable, but it's possible to make things that kinda aren't, like this:

  arc> ($:define-­struct foo (dumm­y) #:pro­perty prop:­equal+hash­ (list­ (lamb­da args #t) (lamb­da args (erro­r "Can'­t prima­ry hash this.­")) (lamb­da args (erro­r "Can'­t secon­dary hash this.­"))))
  #<void>
  arc> (= my-ta­ble (tabl­e))
  #hash()
  arc> (= my-fo­o $.mak­e-foo!dumm­y-val)
  #<foo>
  arc> (= my-ta­ble.my-foo­ 2)
  Error: "Can't primary hash this."