filter sequence of odd integer elements using bitwise exclusive or

odd_XOR_Filter.py

def lonely_Integer(
  b: list# of int
) -> int:
    so_Far = set()
    answer = 0
    
    for n in b:
      if n in so_Far:
        so_Far.discard(n)
      else:  
        so_Far.add(n)
    
    if len(so_Far) > 0:
      answer = so_Far.pop()
    
    return answer

def lonelyinteger(
  b: list# of int
) -> int:
  """
  >>> 4 ^ 9 ^ 95 ^ 93 ^ 57 ^ 4 ^ 57 ^ 93 ^ 9
  95
  """
  answer = -1#None#0
  #assert len(list(b)) % 2 != 0# odd

  for n in b:
    assert 0 <= n <= 100
    if answer == -1:
      answer = n
    else:  
      answer = answer ^ n


  return answer