[IronPython] Constructors & inheriting from standard .NET classes

[Dino Viehland]

You need to override and call the base __new__ instead of __init__.  .NET has a simpler construction model than Python does and __new__ is what best corresponds to .NET constructors.

class Derived(Test.Base):
    def __new__(cls, i):
        return Test.Base.__new__(cls, i)

d = Derived()


From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Zach Crowell
Sent: Friday, August 21, 2009 4:39 PM
To: users at lists.ironpython.com
Subject: [IronPython] Constructors & inheriting from standard .NET classes

I am unable to inherit from .NET classes which do not define a parameterless constructor.  Is this expected behavior? Is there another way to make this inheritance work?

Here's a simple case.

using System;

namespace Test
{
    public class Base
    {
        public Base(int i)
        {
        }
    }
}

import clr
clr.AddReference('Test')
import Test

class Derived(Test.Base):
    def __init__(self):
        pass

d = Derived()

Traceback (most recent call last):
  File "d:\tmp\class.py", line 9, in d:\tmp\class.py
TypeError: Derived() takes exactly 2 arguments (1 given)