e.g., for a sequence of unknown length, what is the most "Pythonic" way of getting the last n elements?
Obviously I could calculate the starting and ending indices. Is there anything slicker?
Yes, by using negative indices:
last_five = somesequence[-5:]
Negative indices in a slice are relative to the sequence length.
Use negative indexing.
seq[-1]
is the last element of a sequence. seq[-3:]
gives you the last three.