jython-users

[Jython-users] Incompatibility of Python in the JVM

[Joshua F. <jo...@jo...>]

I am looking for a convenient summary of ways in which Python is 
incompatible with the JVM, whether interpreting in Jython or compiling with 
jythonc.

I have identified a few such from the documentation, including a ban on 
Python multiple inheritance, but where can I find a summary? 

Re: [Jython-users] Incompatibility of Python in the JVM

[Kevin B. <kb...@ca...>]

Joshua Fox wrote:
> 
> I am looking for a convenient summary of ways in which Python is
> incompatible with the JVM, whether interpreting in Jython or compiling with
> jythonc.

I'm not entirely sure what you mean. Obviously, if you can run something
in Jython it isn't "incompatible with the JVM"...
 
If you mean, "How do CPython and Jython differ", see:
http://www.jython.org/docs/differences.html

> I have identified a few such from the documentation, including a ban on
> Python multiple inheritance, but where can I find a summary?

You can do Python multiple inheritance in Jython, you just can't do multiple 
inheritance of subclasses of Java classes. (For a variety
of reasons that I don't completely agree with.  :-)  /  :-(  ).  Similar behavior
exists with CPython extension classes.

kb

Re: [Jython-users] Incompatibility of Python in the JVM

[Joshua F. <jo...@jo...>]

Thanks,

I see that Jython does in fact allow mult. inh., but not for inheritance 
from java.

I am wondering if there are any points where the JVM limits the full 
flexible use of Python -- perhaps there are none. Microsoft claims that the 
.NET Common Language Runtime is designed to be cross-language compatible, 
but Jython seems to be good evidence that the JVM has that kind of flexibility.

At 08:01 AM 3/8/2002 -0700, you wrote:


>Joshua Fox wrote:
>
>>a ban on Python multiple inheritance
>
>
>You can use MI if you don't inherit from multiple
>Java classes.  All these uses of MI work correctly:
>
> >>> class A:
>...   def a(self): print 'a'
>...
> >>> class B:
>...   def b(self): print 'b'
>...
> >>> class C(A,B):
>...   pass
>...
> >>> c=C()
> >>> c.a()
>a
> >>> c.b()
>b
> >>> import java
> >>> class D(A,java.lang.Object):
>...   pass
>...
> >>> d=D()
> >>> d.a()
>a
> >>> d.toString()
>'org.python.proxies.__main__$D$0@23b9c1'
> >>> class E(java.lang.Object,java.io.Serializable):
>...   pass
>...
> >>> e=E()
>
>This doesn't:
>
> >>> class F(java.lang.Number,java.util.Date):
>...   pass
>...
>Traceback (innermost last):
>   File "<console>", line 1, in ?
>TypeError: no multiple inheritance for Java classes: java.util.Date and 
>java.lan
>g.Number
>

Re: [Jython-users] Incompatibility of Python in the JVM

[Noel R. <no...@ya...>]

At 11:31 AM 3/9/02, Joshua Fox wrote:
>Thanks,
>
>I see that Jython does in fact allow mult. inh., but not for inheritance 
>from java.
>
>I am wondering if there are any points where the JVM limits the full 
>flexible use of Python -- perhaps there are none. Microsoft claims that 
>the .NET Common Language Runtime is designed to be cross-language 
>compatible, but Jython seems to be good evidence that the JVM has that 
>kind of flexibility.

A few places, but not many.  Although it depends on your definition of JVM 
being the limiting factor -- the fact that the JVM can't run CPython module 
written in C removes a lot of useful libraries.  There is some 
functionality of file objects, and the sys, and os modules in particular 
that is just not offered by the JVM.

There are other CPython/Jython differences, of course, but those are the 
main ones stemming from limitations of the JVM itself, rather than 
differing design decisions.

Hope this helps,

Noel


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