divide list ['a', 'b', 'c', '1', '2', '3'] into three separate list

def div(a):
  x = []
  y = []
  z = []
  for i in a:
    if i.isdigit():
      x.append(i)
    else:
      y.append(i)
  z = x + y
  return z
    
div(['a', 'b', 'c', '1', '2', '3'])