本文介绍了打印所有ctypes“结构”字段内省的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
test.c:
#include <stdio.h>
#include <stdlib.h>
struct s {
char a;
int b;
float c;
double d;
};
struct s *create_struct()
{
struct s *res = malloc(sizeof(struct s));
res->a = 1; res->b = 2; res->c = 3.0f; res->d = 4.0;
return res;
}
test.py:
from ctypes import *
class S(Structure):
_fields_ = [
('a', c_byte),
('b', c_int),
('c', c_float),
('d', c_double)
]
lib = CDLL('./test.so')
create_struct = lib.create_struct
create_struct.restype = POINTER(S)
create_struct.argtypes = []
s_ptr = create_struct()
s = s_ptr.contents
print s._fields_[0][0], s.a
print s._fields_[1][0], s.b
print s._fields_[2][0], s.c
print s._fields_[3][0], s.d
print s.__dict__
输出:
a 1
b 2
c 3.0
d 4.0
{}
I' d想改写上面的python脚本来打印我s结构的每个字段,而不必对每个字段进行显式操作。据我了解,可以使用__dict__属性完成此操作,但是我的属性为空。有没有办法对扩展ctypes.Structure的类执行此操作?
I'd like to adapt the python script above to print each field of my s structure without having to do explicitly for each field. From what I understand, this can be done using the __dict__ attribute but mine is empty. Is there any way to do this for a class that extends ctypes.Structure?
推荐答案
如何使用?
>>> from ctypes import *
>>>
>>> class S(Structure):
... _fields_ = [
... ('a', c_byte),
... ('b', c_int),
... ('c', c_float),
... ('d', c_double)
... ]
...
>>> s = S(1, 2, 3, 4.0)
>>>
>>> for field_name, field_type in s._fields_:
... print field_name, getattr(s, field_name)
...
a 1
b 2
c 3.0
d 4.0
更新
如果结构(或联合)中有一个位域,则迭代 _fields _
会产生3个元组,这将导致 ValueError
。为了防止这种情况,您需要调整代码:
If there is a bitfield in the structure (or union), iterating _fields_
yield a tuple of 3 items which will cause ValueError
. To prevent that you need to adjust the code:
...
for field in s._fields_:
print field[0], getattr(s, field[0])
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