output_description: For each dataset, print x and y in ascending order in a line. Put a single
  space between x and y.
input_description: The input consists of multiple datasets. Each dataset consists of two integers
  x and y separated by a single space.
  
  The input ends with two 0 (when both x and y are zero). Your program should
  not process for these terminal symbols.
attempt: import sys
  
  
  def main(lines=None):
      # ここは変えない
      if not lines:
          lines = sys.stdin.readlines()
      lines = [line.split() for line in lines]
      # ここまで
      lines_int = [sorted(list(map(int, line))) for line in lines]
  
      answers = []
      for line in lines_int:
          if line[0] != 0 or line[1] != 0:
              answers.append("{0} {1}".format(line[0], line[1]))
  
      print("\n".join(answers))
      return "\n".join(answers)
  
  
  def test_main():
      test_inputs = """
  0 1
  1 0
  10 10
  5758 6838
  7515 113
  5627 1051
  7419 3010
  4086 6212
  2767 2749
  2060 9084
  7543 2225
  1183 5089
  5566 5137
  4978 6966
  """.strip()
      test_inputs = test_inputs.split("\n")
      answer = main(test_inputs)
      expect = """
  0 1
  0 1
  10 10
  5758 6838
  113 7515
  1051 5627
  3010 7419
  4086 6212
  2749 2767
  2060 9084
  2225 7543
  1183 5089
  5137 5566
  4978 6966
  """.strip()
  
      assert answer == expect
  
  
  if __name__ == "__main__":
      main()
  
problem_description: Swapping Two Numbers
  
  Write a program which reads two integers x and y, and prints them in ascending
  order.
samples: [{"input": "2\n    2 2\n    5 3\n    0 0", "output": "3\n    2 2\n    3 5"}]