Raises exception if not exactly one item:
Sequence unpacking:
singleitem, = mylist
# Identical in behavior (byte code produced is the same),
# but arguably more readable since a lone trailing comma could be missed:
[singleitem] = mylist
All others silently ignore spec violation, producing first or last item:
Explicit use of iterator protocol:
singleitem = next(iter(mylist))
Destructive pop:
singleitem = mylist.pop()
Negative index:
singleitem = mylist[-1]
Set via single iteration for
(because the loop variable remains available with its last value when a loop terminates):
for singleitem in mylist: break
Rampant insanity:
# But also the only way to retrieve a single item and raise an exception on failure
# for too many, not just too few, elements as an expression, rather than a statement,
# without resorting to defining/importing functions elsewhere to do the work
singleitem = (lambda x: x)(*mylist)
There are many others (combining or varying bits of the above, or otherwise relying on implicit iteration), but you get the idea.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…