inconsistant arg expectations in jython

[Samuele Pedroni]

Hi.

Mark Robinson wrote [on comp.lang.python]:

> I hope it isn't considered inappropriate to post jython questions here!

No, but if you're question is jython related (e.g. related to java
integration)
and not a python general question,
you are better served by jython-users at lists.sf.net

>
> I am running jython 2.1a1 on winNT4 and getting a very unusual error. In
> responce to a getFocus event I attempt to determine  which object
> obtained the focus (in this case a JTextField object) as follows:
>
> e.getComponent().getClass().getName()
>
> At run time I am getting a TypeError exception saying that getName()
> expects 1 arg and is receiving 0. From the Java documentation it would
> seem that getName() doesn't ever take an argument.
> Can anyone tell me if this is implemented differently in jython or if I
> am just making a daft mistake, or where I might be able to find out what
> argument it is expecting (my searching has been fruitless).
>

That's tricky. Let's see

>>> from java.io import File
>>> from java.lang import Object
>>> Object.getName()
'java.lang.Object'
>>> File.getName()
Traceback (innermost last):
  File "<console>", line 1, in ?
TypeError: getName(): expected 1 args; got 0
>>> # ???

That's the very same problem. Why does this happen?
The contents of File.__dict__ masks the contents
File.__class__ .__dict__ , File.__class__ is java.lang.Class
but File has a getName method too, so File.getName
give you an unbound version of that method, that expects
a File argument  (the this/self argument):

>>> f=File('/usr')
>>> File.getName(f)
'usr'

In general when you want to call a method of java.lang.Class
on a Class instance and avoid this kind of clash, you should
use the unbound version:

>>> from java.lang import Class
>>> Class.getName(File)
'java.io.File'

Or using the pythonic classes protocol,
which has an equivalent support at least
for getName:

>>> File.__name__
'java.io.File'

You encounter the problem because java.awt.Component
has a getName method.

regards, Samuele Pedroni.