[Python.NET] Accessing a list that is a read-only property?
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 ServiceHosts
{
get
{
return m_ServiceInformation.ServiceHosts;
}
}
}
public class ServiceInformation
{
public List ServiceHosts { get; set; }
public ServiceInformation()
{
ServiceHosts = new List();
}
}
}
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 "", line 1, in
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 "", line 1, in
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 "", line 1, in
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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[Python.NET] How do you add an element to a List in a read-only property?
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 ServiceHosts
{
get
{
return m_ServiceInformation.ServiceHosts;
}
}
}
public class ServiceInformation
{
public List ServiceHosts { get; set; }
public ServiceInformation()
{
ServiceHosts = new List();
}
}
}
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 "", line 1, in
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 "", line 1, in
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 "", line 1, in
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
___
PythonNet mailing list -- [email protected]
To unsubscribe send an email to [email protected]
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[Python.NET] Re: Accessing a list that is a read-only property?
Hi Mark, You are facing https://github.com/pythonnet/pythonnet/issues/514 At this moment the easiest way to do it is to add a method to ServiceInformation to add an item to SerivceHosts collection. E.g. public void AddServiceHost(string serviceHost) => this.ServiceHosts.Add(serviceHost); then call it from Python. Regards,Victor From: Mark BrightonSent: Tuesday, March 3, 2020 10:42 AMTo: [email protected]: [Python.NET] Accessing a list that is a read-only property? 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 ServiceHosts { get { return m_ServiceInformation.ServiceHosts; } } } public class ServiceInformation { public List ServiceHosts { get; set; } public ServiceInformation() { ServiceHosts = new List(); } }} 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 "", line 1, in 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 = hostsTraceback (most recent call last): File "", line 1, in 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 "", line 1, in 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___PythonNet mailing list -- [email protected] unsubscribe send an email to [email protected]://mail.python.org/mailman3/lists/pythonnet.python.org/ ___ PythonNet mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/pythonnet.python.org/
