Now we can proceed with implementing a simple booking system. For each flight we simply need to keep track of who is sitting in each seat. We'll represent the seat allocations using a list of dictionaries. The list will contain one entry for each seat row, and each entry will be a dictionary mapping from seat-letter to occupant name. If a seat is unoccupied, the corresponding dictionary value will contain None.

We initialize the seating plan in Flight.__init__() using this fragment:

rows, seats = self._aircraft.seating_plan()
self._seating = [None] + [{letter: None for letter in seats} for _ in rows]

In the first line we retrieve the seating plan for the aircraft and use tuple unpacking to put the row and seat identifiers into local variables rows and seats. In the second line we create a list for the seat allocations. Rather than continually deal with the fact that row indexes are one-based whereas Python lists use zero-based indexes, we choose to waste one entry at the beginning...