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Problematic behavior of the import statement when several module files have the same name.

P: n/a
Xif
Hello Everyone!

Here's a problem with relative imports:

Suppose I have a package called some_package (in a separate directory
included in the PYTHONPATH, with an __init__.py file etc.)

This package has a module inside the directory, called "database", and
therefore residing in the file some_package/database.py.

Now, what if there's another module, for example inside the
site-packages directory, with the same file name (i.e. database.py)?

We have a problem. Since although these modules have different absolute
names ("some_package.database" for the first module, and just
"database" for the second), when I try to do

import database

from inside some_package, it first of all tries to find the matching
file in the some_package directory (i.e. do a relative import). Since
it first checks the some_package directory, and finds database.py
there,

import database

in fact imports the module with the absolute name
some_package.database.

This is problemat on two levels:

1) It is surprising and undesirable that "import database" in effect
may do two completely different things ("import some_package.database"
or "import database") depending on an external, unpredictable factor:
the existence of a database.py file inside the some_package directory.

2) It effectively prevents you from naming a module inside a package
with the same name of any module in the "root" PYTHONPATH directories.
In my example, there's no sane way I can see of having
some_package.database if there's already a database module (database.py
file) in any PYTHONPATH directory.

Are my observations correct? Is there something I ignored? Should
this be posted somewhere else?

Your comments would be appreciated.

Xif

Jul 18 '05 #1
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P: n/a
Xif wrote:
Hello Everyone!

Here's a problem with relative imports:

Suppose I have a package called some_package (in a separate directory
included in the PYTHONPATH, with an __init__.py file etc.)

This package has a module inside the directory, called "database", and
therefore residing in the file some_package/database.py.

Now, what if there's another module, for example inside the
site-packages directory, with the same file name (i.e. database.py)?

We have a problem. Since although these modules have different absolute
names ("some_package.database" for the first module, and just
"database" for the second), when I try to do

import database

from inside some_package, it first of all tries to find the matching
file in the some_package directory (i.e. do a relative import). Since
it first checks the some_package directory, and finds database.py
there,

import database

in fact imports the module with the absolute name
some_package.database.


You've just re-discovered the reason you should always use absolute
imports. Check out:

http://www.python.org/doc/faq/progra...rt-in-a-module

STeVe
Jul 18 '05 #2

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