Jython

Hi guys,

As I go through the steep learning curve getting to grips with Jython I 
thought it would be helpful for other future contributors if I blogged 
about my personal progress and record the many stumbling blocks I will 
no doubt encounter along the way.  Here's the link:

http://gushieblog.blogspot.com/

Please let me know (via a blog comment) if I have made any mistakes in 
this first entry.

Thanks.
Paul

Hi,

I was looking at the ClassDictInit interface.  Its a
marker interface that is supposed to indicate that
there is a static method called classDictInit and that
it needs to be invoked so the dict can be populated. 
On the other hand there appears to be a parallel
static method poping up over the place, typeSetup
which is also used apparently to populate a "dict". 
In other words, they look very similiar in purpose.

Oddly in some cases, it appears that the class
implements the interface(PyTuple, PyString) and the
method but the empty method is never invoked. 
__builtin__ implements it and the method is invoked.

maybe their purpose is different enough to warrant the
division?
leouser




 
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Hi,

I was peeking at InternalTables1 and noticed it
defined this fine interface:
    protected static interface Table {

        public Object put(Object key, Object obj);



        public Object get(Object key);



        public Object remove(Object key);



        public void clear();

    }


---------------
It usage appears to be in InternalTables1 and
InternalTables2.  One case is used to extends
Hashtable the other to extend HashMap.  Now this
interface appears to be a subset of the Map interface.
 Given that both of its implementors are Map
implementors, would it not make sense to get rid of it
and its subclasses and just rely on the Map
interface?(Maybe it will happen if all the *1 and *2
classes are unified).  This has got to be an artifact
of 1.1 support.

leouser



 
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After a little further digging, I now realise that Jython reflectively 
determines whether a method supports keyword arguments by checking 
whether it has a PyObject[] and String[] for parameters.

Oh well, that's something else I have learned!  I am getting there, 
gradually :)

Paul Drummond wrote:
> Hi Guys,
> 
> I have been spending what little spare time I have looking at the csv 
> module.  I'm afraid I haven't got very far yet as I am currently smack 
> bang in the middle of a very steep learning curve!  I am making progress 
> however and am still as keen as ever!
> 
> Currently, I am trying to understand the correct way to parse the 
> arguments for csv.reader().  The method's definition from the python 
> library docs is:
> 
> reader(csvfile[, dialect='excel'[, fmtparam]])
> 
> As csvfile is mandatory I thought it would be okay to specify it 
> explicitly in my method signature, then use optional arguments for the 
> rest.  With a little help from the Wiki FAQ I ended up with this:
> 
> public static PyObject reader(PyObject iterableObject, PyObject[] args, 
> String[] keywords) {
> }
> 
> But here is where I get confused because now Jython *EXPECTS* 3 
> arguments which is not how Python behaves:
> 
>  >>> import csv
>  >>> csv.reader()
> Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
> TypeError:  expected at least 1 arguments, got 0
> 
> jython:
>  >>> import csv
>  >>> csv.reader()
> Traceback (innermost last):
>    File "<console>", line 1, in ?
> TypeError: reader(): expected 3 args; got 0
>  >>>
> 
> So to make csv.reader() behave the same as python, I'd need to pass an 
> array of PyObjects into reader() then use ArgParser and do my own type 
> checking and error handling:
> 
> public static PyObject reader(PyObject[] args) {
>     //Use ArgParser and my own error handling to throw if there isn't
>     //at least one argument + other checks.
> }
> 
> I guess it's easier to explicitly specify arguments when the module 
> hides behind a python wrapper then you already know the number of 
> arguments the wrapper uses.  I can't do this for csv as the reader() 
> method is exposed directly through the csv.py wrapper so it must support 
> dynamic arguments.
> 
> Does all of this make sense or am I getting it completely wrong?
> 
> Cheers,
> Paul.
> 
> 
> 
> 
> 
> 
> 
> 
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