python ctypes的byref和pointer有啥区别

byref(n)返回的相当于C的指针右值&n，本身没有被分配空间：

>>> from ctypes import *
>>> n = c_int(0)
>>> p = byref(n)
>>> pp = byref(p)
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    pp = byref(p)
TypeError: byref() argument must be a ctypes instance, not ‘CArgObject‘

pointer返回的相当于指针左值T* p=&n，可以改变，可以取地址:

>>> from ctypes import *
>>> n = c_int(0)

>>> q = pointer(n)
>>> q.contents = c_int(1)
>>> qq = byref(q)
>>> dir(qq)
[‘__class__‘, ‘__delattr__‘, ‘__dir__‘, ‘__doc__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__gt__‘, ‘__hash__‘, ‘__init__‘, ‘__le__‘, ‘__lt__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__setattr__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘_obj‘]
>>> type(qq)
<class ‘CArgObject‘>                  #‘CArgObject‘是什么对象？？？

>>> qq
<cparam ‘P‘ (010AD238)>
>>> q
<__main__.LP_c_long object at 0x010AD210>
>>> q.contents
c_long(1)

对于T**参数，通常你得构造一个pointer，然后byref传进去

以__开头并以__结束的属性（__class__、__dir__ 等）都是为内置方法（built-in method），唯独_obj不是

>>> qq._obj
<__main__.LP_c_long object at 0x010B8120>
>>> q
<__main__.LP_c_long object at 0x010B8120>

由以上执行代码可知，二维指针qq的_obj属性就是该二维指针的首地址，即指向q指针的地址

PS: addressof返回一个Python整数，不能直接传给C那边

python ctypes的byref和pointer有啥区别

原文：http://www.cnblogs.com/fendou-999/p/3527449.html