将ctypes.POINTER（instance）转换为实际实例？

Question

我有以下ctypes函数，该函数接受文件名并返回指向Image实例的指针：

class Image(ctypes.Structure):
  _fields_ = (
      ('image_info', ImageInfo),
      ('type', ctypes.c_int),
      ('format', ctypes.POINTER(Format) ),
  )
my_image_open = _lib.my_image_open
my_image_open.argtypes = [ ctypes.c_char_p ]
my_image_open.restype = ctypes.POINTER(Image)

我想提供一些语法糖，并将my_image_open包装在Image构造函数中。 但是我不能简单地将返回的指针绑定到self ：

class Image(ctypes.Structure):
  def __init__( self, filename ):
    img = my_image_open( filename )
    self = img[0] # does not work, since self is local !

进行上述操作是否有意义，还是我应该只留下一个返回实例的独立函数：

c_image_open = _lib.my_image_open
c_image_open.argtypes = [ ctypes.c_char_p ]
c_image_open.restype = ctypes.POINTER(Image)
# syntactic sugar:
def my_image_open( filename ):
  img = c_image_open( filename )
  return img[0]

Answer 1

所以我最终遵循了@eryksun的建议：

class Image(ctypes.Structure):
  _fields_ = (
      ('image_info', ImageInfo),
      ('type', ctypes.c_int),
      ('format', ctypes.POINTER(Format) ),
  )
  @classmethod
  def open(cls,filename):
    img = my_image_open( filename )
    if img: return img[0]
    return None