[Python-Dev] New relative import issue (original) (raw)

Josiah Carlson jcarlson at uci.edu
Tue Sep 19 06🔞24 CEST 2006

Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Armin Rigo wrote: > there > is no clean way from a test module 'foo.bar.test.testhello' to import > 'foo.bar.hello': the top-level directory must first be inserted into > sys.path magically.

I've felt for a long time that problems like this wouldn't arise so much if there were a closer connection between the package hierarchy and the file system structure. There really shouldn't be any such thing as sys.path -- the view that any given module has of the package namespace should depend only on where it is, not on the history of how it came to be invoked.

Wait, wait, wait. If I remember correctly, one of the use-cases cited was for sub-packages of a single larger package to be able to import other sub-packages, via 'from ..subpackage2 import module2'. That is to say, given a package structure like...

.../init.py .../subpackage1/module1.py .../subpackage1/init.py .../subpackage2/module2.py .../subpackage2/init.py

Running module1.py, with an import line that read: from ..subpackage2 import module2

... would import module2 from subpackage2

Testing this in the beta I have installed tells me:

Traceback (most recent call last): File "module1.py", line 1, in from ..subpackage2 import module2 ValueError: Relative importpath too deep

While I can understand why this is the case (if one is going to be naming modules relative to main or otherwise, unless one preserves the number of leading '.', giving module2 a name of main..subpackage2.module2 or ..subpackage2.module2, naming can be confusing), it does remove a very important feature.

Guido suggested I make up a PEP way back in March or so, but I was slowed by actually implementing main-relative naming (which is currently incomplete).

As it stands, in order to "work around" this particular feature, one would need to write a 'loader' to handle importing and/or main() calling in subpackage1/module1.py .

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