Why does "T" occur twice in the list-which-is-actually-a-tuple? And why is there a comma after the second occurrence of "T" in that tuple?

this list: ("T","R","W","A","G","M","Y","F","P","D","X","B","N","J","Z","S","Q","V","H","L","C","K","E","T",)

Did you just reinvent the String here? Would "TRWAGMYFPDXBNJZSQVHLCKET" work just as well?

Trivial exercise with zero novelty and educational value.

Please refer to Creating your first kata for guidelines on how to author a proper Kata.