[Python-Dev] Re: Jython bugs or features? (original) (raw)

Samuele Pedroni pedronis@bluewin.ch
Mon, 25 Feb 2002 21🔞36 +0100

[Dinu Gherman]

I'm pretty surprised! I knew the Python test suite is very far from complete, but list() is an extremely crucial function, isn't it?

Given how things concretely are and not considering some abstract point of view, I would say YMMV.

I have skimmed over CPython 2.1 std lib, honestly there are not many places relevant to Jython where list for copying lists is used and where the bug can show through. Consider things like:

a += list(b) OR b = ... + list(b)

and all the places where l = list(sq) and sq is not a list, those works in Jython.

Btw here simply Jython was never up to speed (that means always implemented the wrong semantics) and nobody noticed this or to be precise ever reported this.

OTOH we try to be responsive to bug reports.

Yes the test suites are far from optimal and CPython sometimes regresses too.

My impression is that Jython claims to be an implementation of Python in Java.

Yes but your PS (see below) shows that this can mean a lot of things, Jython is more about writing new programs and Java integration (which is a big and non-easy part and of its codebase) than for example supporting completely CPython os and shell-like programming and allowing effortless porting of all kinds of CPython programs (clearly list bug is another kind of issue given that the right behaviour is well documented).

Java integration has a higher priority than those thing. Jython is more about embracing the Java platform (philosophy) than work-arounding it. For example anything that would require writing JNI glue and native C code is simply discarded.

There are things for which CPython is simply better suited than Java/Jython and the other way around.

They are not fully equivalent substitutes.

Everybody understands the existence of bugs, but if functions are missing I'm not sure there is sufficient quality control, leave alone a useful test suite.

My bold guess is that it should be very easy to check automatically for each module in the std.lib. at least if the same classes and methods do exist in CPython and JPython. Honestly, I don't think it makes much sense to maintain two code bases without some degree of automatic testing...

JPython is not born with such a test, and Jython until now has never grown one. But I have taken note of this adding a feature request for such a test but is more a matter of resources and priorities than easiness.

Btw after some checking of the CPython CVS

http://groups.google.com/groups?q=g:thl2649249624d&hl=en&selm=mailman.100742 5027.30019.python-list%40python.org

(look at the change in the module-level doc )

it seems that reset is vestigial and one should use seek(0) instead.

reset is not supported by StringIO or by files and not documented (not after 1.5 for sure).

You made me think that it was added in 2.1, so at least IMO it is an option for Jython to have decided not to support it.

When seeing such bugs, my immediate reaction (like that of most others) is to think that not many people can be using this serious- ly.

See e.g.: http://groups.google.com/groups?q=g:thl2649249624d&hl=en&selm=mailman.100742 5027.30019.python-list%40python.org and thread.

PS: BTW, how about this one:

[localhost:~] dinu% jython Jython 2.1 on java1.3.1 (JIT: null) Type "copyright", "credits" or "license" for more information. >>> import os >>> os.chdir('..') Traceback (innermost last): File "", line 1, in ? File ".../Jython-2.1/Lib/javaos.py", line 56, in chdir OSError: [Errno 0] chdir not supported in Java: ..

We don't support this one, sorry.