[Python-Dev] Import semantics (original) (raw)

Guido van Rossum guido at python.org
Mon Jun 12 18:48:45 CEST 2006

On 6/12/06, Samuele Pedroni <pedronis at strakt.com> wrote:

Fabio Zadrozny wrote: > Python and Jython import semantics differ on how sub-packages should be > accessed after importing some module: > > Jython 2.1 on java1.5.0 (JIT: null) > Type "copyright", "credits" or "license" for more information. > >>> import xml > >>> xml.dom > <module xml.dom at 10340434> > > Python 2.4.2 (#67, Sep 28 2005, 12:41:11) [MSC v.1310 32 bit (Intel)] on > win32 > Type "help", "copyright", "credits" or "license" for more information. > >>> import xml > >>> xml.dom > Traceback (most recent call last): > File "", line 1, in ? > AttributeError: 'module' object has no attribute 'dom' > >>> from xml.dom import pulldom > >>> xml.dom > <module 'xml.dom' from 'C:\bin\Python24\lib\xml\dom_init_.pyc'> > > Note that in Jython importing a module makes all subpackages beneath it > available, whereas in python, only the tokens available in init.py > are accessible, but if you do load the module later even if not getting > it directly into the namespace, it gets accessible too -- this seems > more like something unexpected to me -- I would expect it to be > available only if I did some "import xml.dom" at some point. > > My problem is that in Pydev, in static analysis, I would only get the > tokens available for actually imported modules, but that's not true for > Jython, and I'm not sure if the current behaviour in Python was expected. > > So... which would be the right semantics for this?

the difference in Jython is deliberate. I think the reason was to mimic more the Java style for this, in java fully qualified names always work. In jython importing the top level packages is enough to get a similar effect. This is unlikely to change for backward compatibility reasons, at least from my POV.

IMO it should do this only if the imported module is really a Java package. If it's a Python package it should stick to python semantics if possible.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

More information about the Python-Dev mailing list