def testRepeatedScalarFieldSortArguments(self, message_module):
    """Check sorting a scalar field using list.sort() arguments."""
    message = message_module.TestAllTypes()

    message.repeated_int32.append(-3)
    message.repeated_int32.append(-2)
    message.repeated_int32.append(-1)
    message.repeated_int32.sort(key=abs)
    self.assertEqual(list(message.repeated_int32), [-1, -2, -3])
    message.repeated_int32.sort(key=abs, reverse=True)
    self.assertEqual(list(message.repeated_int32), [-3, -2, -1])
    if sys.version_info < (3,):  # No cmp sorting in PY3.
      abs_cmp = lambda a, b: cmp(abs(a), abs(b))
      message.repeated_int32.sort(sort_function=abs_cmp)
      self.assertEqual(list(message.repeated_int32), [-1, -2, -3])
      message.repeated_int32.sort(cmp=abs_cmp, reverse=True)
      self.assertEqual(list(message.repeated_int32), [-3, -2, -1])

    message.repeated_string.append('aaa')
    message.repeated_string.append('bb')
    message.repeated_string.append('c')
    message.repeated_string.sort(key=len)
    self.assertEqual(list(message.repeated_string), ['c', 'bb', 'aaa'])
    message.repeated_string.sort(key=len, reverse=True)
    self.assertEqual(list(message.repeated_string), ['aaa', 'bb', 'c'])
    if sys.version_info < (3,):  # No cmp sorting in PY3.
      len_cmp = lambda a, b: cmp(len(a), len(b))
      message.repeated_string.sort(sort_function=len_cmp)
      self.assertEqual(list(message.repeated_string), ['c', 'bb', 'aaa'])
      message.repeated_string.sort(cmp=len_cmp, reverse=True)
      self.assertEqual(list(message.repeated_string), ['aaa', 'bb', 'c'])