something wrong with my pythonpath

Question

I know this is a dumb question but i'm stumped. My directory structure used to look like this:

-src
 |
 -module.py
 -program.py

when this what my directory structure, I referenced module from program and all was well.

I've since changed my directory structure to this:

-src
 |
 -__init.py
 -module.py
 |
 -programDir
 |
 -__init.py
 -program.py

now, of course, I can't reach the module from program. How can I reference src as a package. I tried to create an

__init__.py 

file in the src directory, but no luck.

Moar deets: import statements i've tried in program.py:

import module

and

from src import module

the first one worked when the other module and program were in the same directory.

error i'm getting:

ImportError: No module named module

and just for the record: No, my module and program are not called module OR program

update: I've tried this in my program.py file:

from ...src import module

and

from ..src import module

both are giving me:

ValueError: Attempted relative import in non-package

• user395760: Moar details! For instance, how the import statements look and what errors you get.

Answer 1

For starters, I recommend reading the entry Modifying Python's Search Path in the docs.

It might be frowned upon by some, but if you wish to modify the PYTHONPATH from within your program, according to the documentation's standard modules entry you can use the sys.path.append method:

import sys
sys.path.append('..')
import module

• Ramy: well this works. I was hoping for something a little more elegant - like something in the way of creating a package - but this works for now.

Answer 2

Couldn't you use PEP 328 to solve this?

• Ramy: this looks promising. I'll have to play around with it tomorrow and let you know how it goes.
• Ramy: could you check out my latest edits? I still seem to be getting a ValueError
• Ramy: just realized I'm using ironPython. Not sure if this'll work for IPy.
• Bill Lynch: Dumb question here, are you creating __init__.py or __init.py in those directories?

Answer 3

If you run program.py directly, with python program.py or with #!, then module.py's directory should be in the PYTHONPATH for import module to work. This can be achieved using a helper shell script that's kept in programDir, for instance, and looks something like:

#!/bin/bash
script_dir=`dirname 0ドル`
# Add the script's parent directory to the PYTHONPATH
export PYTHONPATH=$PYTHONPATH:$script_dir/..
python $script_dir/program.py

Another, probably better, way would be to have program.py export a "main()" function, and create a helper python script at src/program that looks like:

#!/usr/bin/env python
from programDir.program import main
main()

In this case, you can use relative imports in src/programDir/program.py, so this should work:

from .. import module

• Ramy: do you mean src/programDir? I'm not sure I understand this.

Answer 4

The first one worked because Python's sys.path's first entry is '' which means it will look for module names in the current working directory from which you've executed the Python interpreter.

The issue you seem to have is that the directory located at src is not set on your PYTHONPATH. So, you can do is set the PYTHONPATH environment variable explicitly.

Here's an example using bash:

export PYTHONPATH=PATH_TO_SRC:${PYTHONPATH}

then run your program as normal

Another approach is that you can explicitly set sys.path by appending to it upon execution of your program.

So, in your program.py, you would have:

if __name__ == '__main__':
 import os
 import sys
 sys.path.append(os.path.dirname(os.path.dirname(__file__)))
 your_main_function()

Lastly, for serious python development, you should consider virtualenv and virtualenvwrapper as it will take care of most of these things for you.

Answer 5

You need to add __init__.py to /programDir to interpret the directory as a package. Once a package, you can import the package's contents.

So, in your case, if /src is on the PYTHONPATH, from module.py you can import program.py with from programDir import program.

• Ramy: but it's the other way around I want to do it. I want to import module from program. so in program.py, i'm trying to do "import module"
• Filip Dupanović: If /src is in the PYTHONPATH you can do import module. If not, add an __init__.py and you can do a relative import from program.py: from .. import module

Answer 6

If you use program as part of a package, in another python module, such as

import src.programDir.program as p
p.some_method()

you can use relative import in program.py, assuming you are creating a package with src (__init__.py in both src and programDir)

from .. import module

If not, for example you are calling program.py from the command line, you must add the directory containing src to your search path either by modifying sys.path or the PYTHONPATH env var, before importing.