Mailman 3 March 2020 - Python.NET

DLL Processor compatibility
by Govil Nag 04 Mar '20

04 Mar '20

hallo, pythonnet dll work either x64 bit processor or x86 processor ..is it possible to run it in visual Studio with "Any CPU"

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Accessing a list that is a read-only property?
by Mark Brighton 03 Mar '20

03 Mar '20

Hello, I think this is a really basic question, but despite searching I haven't found a solution. I've been asked to use a .NET assembly from python. I have programed in other languages, but not C#. In the brief time I've used it, PythonNet has been fantastic... with one little wrinkle. Here's a pared down version of the C# that I’m trying to access from Python: namespace Service.API { public class ServiceAPI { private static ServiceAPI m_Instance = new ServiceAPI(); public static ServiceAPI Instance { get { return m_Instance; } } public ServiceAPI() { } ~ServiceAPI() {} ServiceInformation m_ServiceInformation = new ServiceInformation(); public List<string> ServiceHosts { get { return m_ServiceInformation.ServiceHosts; } } } public class ServiceInformation { public List<string> ServiceHosts { get; set; } public ServiceInformation() { ServiceHosts = new List<string>(); } } } I need to add strings to the List “ServiceHosts”, accessing it via a ServiceAPI object. The author placed the List inside another class, "ServiceInformation" and did not provide a set accessor, so that the ServiceHosts could not be altered to another object, while allowing strings to be added and removed from it. I think adding a string to that list is trivial in C#: ServiceAPI.Instance.ServiceHosts.Add('1.1.1.1'); So I try it in Python: >>> import clr # Pyton.NET package >>> clr.AddReference("Service.API") >>> import Service.API >>> import System >>> Service.API.ServiceAPI.Instance.ServiceHosts.Add('1.1.1.1') Traceback (most recent call last): File "<interactive input>", line 1, in <module> AttributeError: 'ServiceAPI' object has no attribute 'Add' This is a List that PythonNet is mapping onto a python list: >>> Service.API.ServiceAPI.Instance.ServiceHosts [] So try using a python method: >>> Service.API.ServiceAPI.Instance.ServiceHosts.append('1.1.1.1') >>> Service.API.ServiceAPI.Instance.ServiceHosts [] Nope. And I start suspecting that I've added that string to a boxed version of the list. But because there's no set accessor, I can't do this: >>> hosts = Service.API.ServiceAPI.Instance.ServiceHosts >>> hosts.append('1.1.1.1') >>> Service.API.ServiceAPI.Instance.ServiceHosts = hosts Traceback (most recent call last): File "<interactive input>", line 1, in <module> TypeError: property is read-only So what about calling the unbound list method, passing in the list? >>> System.Collections.Generic.List[String].Add( Service.API.ServiceAPI.Instance.ServiceHosts, '1.1.1.1') Traceback (most recent call last): File "<interactive input>", line 1, in <module> AttributeError: 'ServiceAPI' object has no attribute 'Add' The author of this assembly has offered to create a specific method so that I can access the list, but he assures me that this is a common C# pattern that I will encounter frequently. I can't just create an instance of ServiceInformation and add the hosts to that, ServiceAPI has no method for getting or setting m_ServiceInformation. Any help in setting me in the right direction would be appreciated. Thanks, Mark Brighton

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How do you add an element to a List in a read-only property?
by mark＠brightsoftwaredesign.com 02 Mar '20

02 Mar '20

Hello, I think this is a really basic question, but I haven't found a solution. I've been asked to use a .NET assembly from python. I have programed in other languages, but not C#. In the brief time I've used it, PythonNet has been fantastic... with one little wrinkle. Here's a pared down version of the C#: namespace Service.API { public class ServiceAPI { private static ServiceAPI m_Instance = new ServiceAPI(); public static ServiceAPI Instance { get { return m_Instance; } } public ServiceAPI() { } ~ServiceAPI() {} ServiceInformation m_ServiceInformation = new ServiceInformation(); public List<string> ServiceHosts { get { return m_ServiceInformation.ServiceHosts; } } } public class ServiceInformation { public List<string> ServiceHosts { get; set; } public ServiceInformation() { ServiceHosts = new List<string>(); } } } I need to add strings to the List "ServiceHosts" in ServiceAPI. The author placed the List inside another class, "ServiceInformation" and did not provide a set method, so that the ServiceHosts could not be altered to another object, while allowing strings to be added and removed from it. I think adding a string to that list is trivial in C#: (I've been assured by the assembly author that this works) ServiceAPI.Instance.ServiceHosts.Add('1.1.1.1'); So I try it in Python: >>> import clr # Pyton.NET package >>> clr.AddReference("Service.API") >>> import Service.API >>> import System # This is a .NET package. >>> Service.API.ServiceAPI.Instance.ServiceHosts.Add('1.1.1.1') Traceback (most recent call last): File "<interactive input>", line 1, in <module> AttributeError: 'ServiceAPI' object has no attribute 'Add' This is a List that PythonNet is mapping onto a python list: >>> Service.API.ServiceAPI.Instance.ServiceHosts [] So try using a python method: >>> Service.API.ServiceAPI.Instance.ServiceHosts.append('1.1.1.1') >>> Service.API.ServiceAPI.Instance.ServiceHosts [] Nope. And I start suspecting that I've added that string to a boxed version of the list. But because there's no set accessor, I can't do this: >>> hosts = Service.API.ServiceAPI.Instance.ServiceHosts >>> hosts.append('1.1.1.1') >>> Service.API.ServiceAPI.Instance.ServiceHosts = hosts Traceback (most recent call last): File "<interactive input>", line 1, in <module> TypeError: property is read-only So what about calling the unbound list method, passing in the list? >>> System.Collections.Generic.List[String].Add( Service.API.ServiceAPI.Instance.ServiceHosts, '1.1.1.1') Traceback (most recent call last): File "<interactive input>", line 1, in <module> AttributeError: 'ServiceAPI' object has no attribute 'Add' The author of this assembly has offered to create a specific method so that I can access the list, but he assures me that this is a common C# pattern that I will encounter frequently. I can't just create an instance of ServiceInformation and add the hosts to that, ServiceAPI has no method for getting or setting m_ServiceInformation. Any help in setting me in the right direction would be appreciated. Thanks, Mark Brighton

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