RE: [Jython-users] Supporting + on Java objects

[brian z. <bz...@zi...>]

Anthony,

Try:

  print "text" + str(obj)

for the first one to work.  The reason the latter works is because you
are not concatenating the values only printing them in order.

Python is a strongly typed language and typecasts do not occur
automatically for such operations as adding a string to an integer.  I
do not expect the Jython implementation to change this behaviour.  A
CPython session exhibits the same:

Python 2.2 (#28, Dec 21 2001, 12:21:22) [MSC 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> obj = 1
>>> print "text" + obj
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: cannot concatenate 'str' and 'int' objects
>>>

If you search the c.l.python newsgroup for 'adding string integer'
you'll find a number of references to this issue.

hope this helps,

brian

> -----Original Message-----
> From: jyt...@li... 
> [mailto:jyt...@li...] On Behalf 
> Of Anthony Eden
> Sent: Tuesday, March 26, 2002 12:23 PM
> To: jyt...@li...
> Subject: [Jython-users] Supporting + on Java objects
> 
> 
> Currently, in Jython, using any arbitrary Java object aside 
> from a java.lang.String, the following fails:
> 
>   print "text" + obj
> 
> With the message: TypeError: __add__ nor __radd__ defined for 
> these operands
> 
> But the following works:
> 
>   print "test", obj
> 
> 
> Would the Jython implementers consider modifying the 
> PyJavaInstance class with something similar to:
> 
>     public PyObject __add__(PyObject object) {
>     	return __str__ + object.__str__();
>     }
> 
> So that the + notation as used in Java works properly?  I am 
> not sure if the code I provided above is correct as I am not 
> intimately familiar with the Jython source.  I am also not 
> sure if this has been discussed before: the mailing list 
> archives provided at the Jython.org site do not have search 
> facilities (AFAICT) and I was unable to find anything about 
> it in my mail application (back to 7/21/2001), so I apologize 
> ahead of time if it has.
> 
> Sincerely,
> Anthony Eden
> 
> 
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