How to delegate all method calls to C# DLL in Python

Question

I want to delegate all method call to C# DLL that we have written. I am using pythonnet to load the DLL file and call the methods from the DLL.

This is my python class and it works fine,

import clr
clr.AddReference('MyDll')
from MyDll import MyLibrary


class MyProxy:
    def __init__(self):
        self.lib = MyLibrary()

    def method1(self, first_arg, *args):
        self.lib.method1(first_arg, args)

    def method2(self, first_arg, *args):
        self.lib.method2(first_arg, args)

But I am not doing anything in python code except making a call to dll methods, so I don't want to write wrapper methods for all the methods in dll.

The above approach allows me to call python methods like, MyProxy().method1(first_arg, arg2, arg3, arg4), which in turns passes the first_arg as the first argument and arg2, arg3, arg4 as an array in the second argument to self.lib.method1(first_arg, args).

This behavior is necessary for me because all of my C# methods have signature method1(String first_arg, String[] other_args)

How can I achieve this by only implementing __getattr__ in my python class?

I have tried the below approach, but it throws error "No matching methods found",

class MyProxy:
    def __init__(self):
        self.lib = MyLibrary()

    def __getattr__(self, item):
        return getattr(self.lib, item)

Edit: I think, when I wrap a DLL method like this,

def method1(self, first_arg, *args):
    self.lib.method1(first_arg, args)

python takes care of converting other arguments except the first one to an array and pass that array to DLL method. It matches the signature of DLL method(method1(String first_arg, String[] other_args)), since python passes the second argument as an array.

Can we do anything in __getattr__ method to do the array conversion of other arguments except first one and pass on to DLL methods ?

Webservers usually run under very restrictive user accounts. Can the Webserver even see the dll in question? Or the required code from PythonNet? — Christopher
– Christopher, Commented Oct 18, 2018 at 17:03
This is a desktop application and it is run under admin account. First approach works fine, but I don't want to change my python code every time the .net guy adds a new method. — Rahul Virpara
– Rahul Virpara, Commented Oct 18, 2018 at 17:05
Is it definitely failing looking for one of the methods in your DLL? Maybe it's failing when looking some standard python methods. You could try raising AttributeError if item not in ['method1', 'method2']. — Matthew Strawbridge
– Matthew Strawbridge, Commented Oct 20, 2018 at 19:35
@MatthewStrawbridge No, it is able to find the method, but its not able find the matching signature based on how I call the method. — Rahul Virpara
– Rahul Virpara, Commented Oct 21, 2018 at 9:00

Matthew Strawbridge · Accepted Answer · 2018-10-21 16:11:31Z

1

Not tested, but something like this might work:

class MyProxy:
    def __init__(self):
        self.lib = MyLibrary()

    def __getattr__(self, item):
        lib_method = getattr(self.lib, item)
        def _wrapper(first_arg, *args):
            return lib_method(first_arg, args)
        return _wrapper

answered Oct 21, 2018 at 16:11

Matthew Strawbridge

20.8k10 gold badges82 silver badges97 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to delegate all method calls to C# DLL in Python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related