python relative import

Question

I'm trying to make a relative import in python. but I can't understand the syntax and everytime I search for it here in SO, I can't get an answer:

Here is my folder structure:

Root
    libraries
        mylibrary
        __init__
    projects
        project
            myproject.py

and I want to import 'mylibrary' using a relative path, what's the syntax for doing it?

Where do you want to import `mylibrary` from? `myproject.py` I'm guessing. — Chris, Jun 02 '12 at 16:15

score 3 · Accepted Answer · answered Jun 02 '12 at 16:20

3

You have to add the directory to your python path.

import sys
sys.path.append("/libraries")

But I think it might be better to either put the libraries in the folders of the projects that need it or just install them to one of the standard places already in sys.path.

answered Jun 02 '12 at 16:20

camelNeck

99
10

Sorry, I just started learning python, but I wanted to easily use my 'libraries' across multiple projects, not having to copy/paste them each time I create a project, also, I didn't want to put them into PYTHONPATH because when I needed to redistribute them, I would need to go to C:\python and extract from there. – Evandro Silva Jun 02 '12 at 16:22
No problem. This is is perfectly fine and I agree that this might be the better alternative if you wrote the libraries yourself and have to modify them. Else, I still favour to install them. – camelNeck Jun 02 '12 at 16:24

score 3 · Answer 2 · answered Jun 02 '12 at 16:20

3

I don't think it can be done with a simple import statement. What I would do is to append the relative path to your library folder to sys.path like this:

import sys
sys.path.append('../../')
from libraries import mylibrary

Note that this works only if you start the python interpreter from the projects/project directory.

answered Jun 02 '12 at 16:20

silvado

17,202
2
30
46

So what do I have to do to reuse my functions and classes across multiple projects without copy/paste and without PYTHONPATH? – Evandro Silva Jun 02 '12 at 16:25
2

Then I guess your only option is to install them in a standard place. Read about distutils, it is quite simple to use for pure python packages. – silvado Jun 02 '12 at 16:32

score 3 · Answer 3 · answered Jun 02 '12 at 18:25

There is an unfortunate source of confusion with relative imports. When you first learn about them, you think that they allow you to use generally relative file/directory paths to refer to individual files that will be imported. (Or at least, I thought so.) In fact, they only allow you to use relative paths within a package. This means that certain modules within a package can use relative-import syntax when they need to import other modules from within the same package.

In your example, myproject.py is not in the same package as mylibrary, and in fact is not in any package, so there is no way to use relative imports from inside myproject.py . Relative imports just don't apply in that situation.

There are a couple things you can do to get the effect you want. One is to put your libraries in subdirectories of the system site-packages directory. Another is to put .PTH files in the system site-package directory, with those .PTH files containing the paths to the places where your libraries are stored. Another is to use PYTHONPATH to point to directories where you store your libraries.

Thanks for the info, maybe that explains the error I'm getting. :/ — Evandro Silva, Jun 03 '12 at 13:12

python relative import

3 Answers3

Linked