如何在 python.net 中访问 System.Double[,] 对象

Question

I'm running into a python.net problem where I cannot access ac# object in python. My code (writen in python) imports a DLL via the python.net CLR. The python method runs the imported DLL method and processes the return value. The return value is then transformed to standard python types and returned to the caller.

The expected return object structure should look like this, a list of 4 lists with 4 doubles in each list:

[ 
  [0.0, 0.0, 0.0, 0.0], 
  [0.0, 0.0, 0.0, 0.0], 
  [0.0, 0.0, 0.0, 0.0], 
  [0.0, 0.0, 0.0, 0.0],
]

In my code I parse an empty list to System.Runtime.InteropServices.VariantWrapper(), and present that to the DLL / C# method to initialise the return object. The return object yields the following:

result: (True, <System.Double[,] object at 0x00000201CFF944C8>)

The first argument is an acknowledgement of correct execution, the second argument is the list, at least that is what I expect. When printing out the second argument and getting it's length it shows:

data: System.Double[,]
length: 4

Which at least suggest that the list holds the expected 4 elements, which infact should be lists again.

The problem is that an error is thrown when I tried to loop over the inner 4 elements of the list:

TypeError: invalid index value

I tried several different initialising types and for loops over the result, but without any succes.

Can somebody explain what a "System.Double[,]" object should look like or how I can access it.

Below the code:

doubleList = System.Runtime.InteropServices.VariantWrapper([ [], ])
result = dll.method("command", doubleList)
log.debug(f"result: {result}")
log.debug(f"data: {result[1]}")
log.debug(f"length: {result[1].GetLength(0)}")
for i in range(result[1].GetLength(0)):
    log.debug(f"sub: {result[1][i]}")

Answer 1

.NET arrays can be mutlidimensional ( int[,] ) or jagged (eg array of arrays int[][] ). You are getting multidimensional array, and it is indexed like numpy multidimensional arrays, with comma between dimensions.

TL;DR; result[1][dim0, dim1]

Answer 2

I just wanted to share my final solution to the problem for anyone to come across this post.

Although my own comment to LOST's answer is working, I came into a problem when the python list needed to be shared back to the C# DLL. The native python list wasn't readable for the DLL.

I managed to use the C# methods GetValue() and SetValue() on the incoming and outgoing System.Double[,] array. In this particular case I'm working with a 2D array, but the code can be modified to suite other array's.

def PythonToCSharp2Darray(input_list, array_depth=(4, 4)):
    """Convert a python N-List to a C# Array."""
    a = Array.CreateInstance(Double, array_depth[0], array_depth[1])
    for i in range(array_depth[0]):
        for j in range(array_depth[1]):
            a.SetValue(input_list[i][j], i, j)
    return a

def CSharpToPython2Darray(input_array, array_depth=(4, 4)):
    """Convert a C# Array to a N-List."""
    a = []
    a.append([])
    for i in range(array_depth[0]):
        for j in range(array_depth[1]):
            a[i].append(input_array.GetValue(i, j))
        a.append([])
    return a