CLI 第三步：输出与报错各走各的通道

lessons/24/build_cli/03_output.py · 第 30—40 行（当前源码节选）

 30          if args.output:
 31              write_json(args.output, poems)
 32          if args.json:
 33              print(json.dumps(poems, ensure_ascii=False, indent=2))
 34          else:
 35              for poem in poems:
 36                  print("\n".join(poem["lines"]))
 37      except (ValueError, FileNotFoundError) as error:
 38          print(f"提示：{error}", file=sys.stderr)
 39          return 2
 40      return 0