[IronPython] CLR class constructors and arrays

John Messerly jomes at microsoft.com
Tue Jul 31 00:20:14 CEST 2007

For what it's worth, this appears to be fixed in IronPython 2.0 alpha 3:

>ipy paramcalltest.py
args = System.String[]('a', 'b', 'c')
creating ParamCall object:
pc.Joined() => a,b,c

If it's really bothersome we could add it to the 1.1.1 bug list, but in the meantime I'd suggest the workaround Michael mentioned (wrapping the args up in the tuple)


-----Original Message-----
From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Eric Rochester
Sent: Monday, July 30, 2007 1:37 PM
To: IronPython Users
Subject: [IronPython] CLR class constructors and arrays


I've been using IronPython for a few months now, and I'm really enjoying it. Thanks for all the hard work that's gone into it.

I recently ran across an issue, and I wondered if anyone else has seen it. I think it's probably a bug, but I couldn't find a bug report, either.

Basically, if there is a CLR class that takes an array as its only constructor argument, IronPython always tries to call it using params. For example, if I compile this to ParamCall.dll:
// ParamCall.cs

using System;

namespace ParamCall
    public class ParamCall
        private string[] args;

        public ParamCall(string[] args)
            this.args = args;

        public string Joined()
            return String.Join(",", args);

And I call it using this script:
# paramcall.py

import clr

from ParamCall import ParamCall
from System import Array

args = Array[str]( ['a', 'b', 'c'] )
print 'args =', args

print 'creating ParamCall object:'
pc = ParamCall(args)
print 'pc.Joined() =>', pc.Joined()


I get these results.
C:\home\eric\src\ase\Lse.Net>IronPython\ipy paramcall.py
args = System.String[]('a', 'b', 'c')
creating ParamCall object:
Traceback (most recent call last):
  File C:\home\eric\src\ase\Lse.Net\paramcall.py, line 7, in Initialize
  File , line 0, in __import__##4
  File C:\home\eric\src\ase\Lse.Net\ParamCall.py, line 15, in Initialize
  File , line 0, in NonDefaultNew##54
TypeError: ParamCall() takes exactly 1 argument (3 given)

I have also tried wrapping the arguments in a tuple and calling it like ParamCall( *(args,) ), but the results are the same.

If anyone has any suggestions for work-arounds or clues as to what I'm doing wrong, I'd be glad to hear them.


Eric Rochester

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