158. join·역순 슬라이스와 포함 여부 필터

1codes = ["k7", "a2", "z9", "m4", "b5"]
2line = "".join(codes)
3back = line[::-1]
4nums = "0123456789"
5out = []
6for ch in back:
7    if ch not in nums:
8        out.append(ch.upper())
9print(back, "".join(out))
10digits = [d for d in line if d in nums]
11print("+".join(digits[::-2]))
12print(sum(int(d) for d in digits if d not in "79"))