[ python-Bugs-1510172 ] Absolute/relative import not working?

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Bugs item #1510172, was opened at 2006-06-21 12:35
Message generated for change (Comment added) made by nnorwitz
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Mitch Chapman (mitchchapman)
>Assigned to: Nick Coghlan (ncoghlan)
Summary: Absolute/relative import not working?

Initial Comment:
Trying to import from a module using dotted import syntax produces 
this exception:

ValueError: Relative importpath too deep

This behavior has been confirmed on Mac OS X 10.4 using the Python 
2.5b1 disk image; and on CentOS 4 using the Python 2.5b1 source 
tarball.

The exception is raised regardless of whether the PYTHONPATH 
environment variable can see the toplevel directory of the package 
being tested; regardless of whether the import is performed from an 
interactive Python session or from a script invoked from the command 
line; and regardless of whether the main script starts with

from __future__ import absolute_import

To test, I tried to re-create the package structure used as an example 
in PEP 328.  (See attachments.)

Most of the files were empty, except moduleX.py and moduleY.py:

#moduleX.py:
from __future__ import absolute_import

from .moduleY import spam

#moduleY.py:
spam = "spam"

According to the PEP, if should be possible to import moduleX without 
error.  But I get the above exception whenever I try to import moduleX 
or to run it from the command line.

$ python2.5 moduleX.py 
Traceback (most recent call last):
  File "moduleX.py", line 3, in <module>
    from .moduleY import spam
ValueError: Relative importpath too deep


Is this a usage/documentation error?


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>Comment By: Neal Norwitz (nnorwitz)
Date: 2006-06-26 21:41

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http://mail.python.org/pipermail/python-dev/2006-June/066197.html

Nick you made mention of changing the docs, but I'm not sure
if you did or not.  Could you address this bug?  Thanks.

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Comment By: Thomas Wouters (twouters)
Date: 2006-06-23 06:52

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See the discussion started at:
http://mail.python.org/pipermail/python-dev/2006-June/066161.html

It's not a bug in 328 or 338 (the PEP that adds the -m
switch for packages), but in the interaction between the
two. I don't think this will be fixed for 2.5, since there
is no obvious fix. If it hurts when you press there, don't
press there. Either don't use -m for packaged modules, or
have the packaged module only use absolute imports. (But
don't be surprised if the script-module is imported twice,
once as __main__ and once as the module itself. That's a
whole other bug/feature.)





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Comment By: Mitch Chapman (mitchchapman)
Date: 2006-06-21 16:57

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Hm... but the same error occurs if one tries to import moduleX from an 
interactive Python session, or from a sibling module.

In other words, in 2.5b1 any module which uses relative imports can be used 
only as a fully-qualified member of a package.  It cannot be imported directly 
by a sibling module, and it cannot be used as a main module at all:

$ python2.5 -m package.subpackage1.moduleX
...
    from .moduleY import spam
ValueError: Relative importpath too deep

Given other efforts (PEP 299; PEP 338) to make it easier to use modules both 
as mainlines and as imports, I still think this is a bug.


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Comment By: Žiga Seilnacht (zseil)
Date: 2006-06-21 15:59

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I think this is a usage error. The problem is that
you run moduleX as a script. This puts the module's
directory as the first entry in sys.path (see
http://docs.python.org/dev/lib/module-sys.html#l2h-5058
for detais).
As a consequence, moduleX is recognised as a top
level module, not as part of a package.

If you want to test relative import, try opening an
interactive shell in the directory where `package`
resides, and type:

>>> from package.subpackage1 import moduleX
>>> moduleX.spam
'spam'


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Comment By: Mark Nottingham (mnot)
Date: 2006-06-21 14:16

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Seeing the same behaviour; OSX with the installer.

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