Python：我们可以将 ctypes 结构转换为字典吗？

Question

我有一个 ctypes 结构。

class S1 (ctypes.Structure):
    _fields_ = [
    ('A',     ctypes.c_uint16 * 10),
    ('B',     ctypes.c_uint32),
    ('C',     ctypes.c_uint32) ]

如果我有 X=S1()，我想从这个对象中返回一个字典：例如，如果我执行类似的操作：Y = X.getdict() 或 Y = getdict(X)，那么 Y 可能看起来像:

{ 'A': [1,2,3,4,5,6,7,8,9,0], 
  'B': 56,
  'C': 8986 }

有什么帮助吗？

Answer 1

大概是这样的：

def getdict(struct):
    return dict((field, getattr(struct, field)) for field, _ in struct._fields_)

>>> x = S1()
>>> getdict(x)
{'A': <__main__.c_ushort_Array_10 object at 0x100490680>, 'C': 0L, 'B': 0L}

如您所见，它适用于数字，但不适用于数组——您必须自己负责将数组转换为列表。尝试转换数组的更复杂的版本如下：

def getdict(struct):
    result = {}
    for field, _ in struct._fields_:
         value = getattr(struct, field)
         # if the type is not a primitive and it evaluates to False ...
         if (type(value) not in [int, long, float, bool]) and not bool(value):
             # it's a null pointer
             value = None
         elif hasattr(value, "_length_") and hasattr(value, "_type_"):
             # Probably an array
             value = list(value)
         elif hasattr(value, "_fields_"):
             # Probably another struct
             value = getdict(value)
         result[field] = value
    return result

如果您有

numpy

并且希望能够处理多维 C 数组，您应该添加

import numpy as np

并更改：

 value = list(value)

至：

 value = np.ctypeslib.as_array(value).tolist()

这将为您提供一个嵌套列表。

Answer 2

处理双精度数组、结构数组和位域的更通用的用途。

def getdict(struct):
    result = {}
    #print struct
    def get_value(value):
         if (type(value) not in [int, float, bool]) and not bool(value):
             # it's a null pointer
             value = None
         elif hasattr(value, "_length_") and hasattr(value, "_type_"):
             # Probably an array
             #print value
             value = get_array(value)
         elif hasattr(value, "_fields_"):
             # Probably another struct
             value = getdict(value)
         return value
    def get_array(array):
        ar = []
        for value in array:
            value = get_value(value)
            ar.append(value)
        return ar
    for f  in struct._fields_:
         field = f[0]
         value = getattr(struct, field)
         # if the type is not a primitive and it evaluates to False ...
         value = get_value(value)
         result[field] = value
    return result

Answer 3

像这样的东西怎么样：

class S1(ctypes.Structure):
    _fields_ = [ ... ]

    def getdict(self):
        dict((f, getattr(self, f)) for f, _ in self._fields_)