Should be around 40% faster according to this simplified small benchmark:
python -m timeit "a=[0, 1, 2, 3, 4];b=list((e if i in {0, len(a) -1} else str(e)) for i, e in enumerate(a))"
200000 loops, best of 5: 1.12 usec per loop
python -m timeit "a=[0, 1, 2, 3, 4];b=list((a[0], *(str(e) for e in a[1:-1]), a[-1]))"
500000 loops, best of 5: 651 nsec per loop
python -m timeit "a=[0, 1, 2, 3, 4,5,6,7,8,9,10,11,12,13,14,15,16];b=list((e if i in {0, len(a) -1} else str(e)) for i, e in enumerate(a))"
100000 loops, best of 5: 3.31 usec per loop
python -m timeit "a=[0, 1, 2, 3, 4,5,6,7,8,9,10,11,12,13,14,15,16];b=list((a[0], *(str(e) for e in a[1:-1]), a[-1]))"
200000 loops, best of 5: 1.72 usec per loop
b922270ce7