Unable to use init.py

Question

I must be missing something simple here.

I have a directory structure:

maths/
    __init__.py
    test.py
    ...

    foo/
       __init__.py
       ...

    bar/
       __init__.py
       ...

In multiple files (but not all) I am using the path of the module - on Ubuntu for example - that path is /home/nebffa/Desktop/maths for some tasks. However, I have to compute the path of the maths package in all of those files - so I thought maybe it will be easier to just have it available via __init__.py. At least that's what I thought I could do based on reading up on __init__.py - maybe I'm wrong?

Anyway, attempts to make things available by putting them in the base __init__.py have failed to work so I think I might be misunderstanding this Python concept.

@Adam The text in `test.py` is literally just `itertools`, which is enough to throw this error. — Waleed Khan, Oct 14 '13 at 03:59
I think you misunderstood `__init__.py`. See http://stackoverflow.com/questions/448271/what-is-init-py-for — laike9m, Oct 14 '13 at 07:21
@laike9m I thought so too, but then it says "execute initialization code for the package" - which is what I am using it for? — nebffa, Oct 14 '13 at 07:24
@nebffa Yes,the initialization code will be executed when the package is imported for the first time. — laike9m, Oct 14 '13 at 07:30

score 1 · Answer 1 · answered Oct 14 '13 at 03:59

1

maths and maths.test are two separate modules, each with their own distinct namespace. You will need to explicitly import itertools in maths.test if you want it available there.

Also, python -m maths.test.

answered Oct 14 '13 at 03:59

Ignacio Vazquez-Abrams

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I thought I could put things in `__init__.py` and they would automatically be imported upon trying to run/import test.py? – nebffa Oct 14 '13 at 04:07
No. Each module has its own distinct namespace. – Ignacio Vazquez-Abrams Oct 14 '13 at 04:07
@nebffa Why don't you just put `import itertools` in `test.py`? – Adam Oct 14 '13 at 04:08
@Adam I actually want to put the overall package's path in __init__.py - I am calling it in a number of places in my package and it is getting annoying. `itertools` is just a simple example I was trying to test. – nebffa Oct 14 '13 at 04:09
@IgnacioVazquez-Abrams `python -m maths.test` returns the exact same error. – nebffa Oct 14 '13 at 04:10
@nebffa: Of course it does. It doesn't magically make what you want work. – Ignacio Vazquez-Abrams Oct 14 '13 at 04:12
@nebffa A python package is a **module**, like any other. The difference is that, instead of having the module file called `module_name.py` it is called `package_name/__init__.py`. Doing `import package` searches for a directory called `package` that contains a `__init__.py` file and builds a **module** out of `__init__.py`. There is *no* special behaviour involved. Since in python there are no such things as "globals", you *always* have to import the things you need in a module, so you have to do when writing a package. – Bakuriu Oct 14 '13 at 07:34

score 1 · Accepted Answer · answered Oct 14 '13 at 04:07

1

If you run python test.py then __init__.py is not involved at all.

answered Oct 14 '13 at 04:07

Adam

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How do I run it so that `__init__.py` is involved? – nebffa Oct 14 '13 at 04:08
You would have to run it on the `maths` folder itself, as a module. – SethMMorton Oct 14 '13 at 04:09
You have to import the entire `maths` module, or import `maths.test` – Adam Oct 14 '13 at 04:10
1

@SethMMorton like `python -m maths.test`? – nebffa Oct 14 '13 at 04:12
@Adam `import maths` works but does not have `itertools` in the namespace. `import maths.test` errors with the same `NameError` as in the question. – nebffa Oct 14 '13 at 04:13
You should edit your question with what you're trying to accomplish. Clearly this isn't your entire project, and any solutions have to work within the larger context. – Adam Oct 14 '13 at 04:15
That's one way to do it. – SethMMorton Oct 14 '13 at 04:15
1

Yeah I just ended up ignoring __init__.py in the end, and made a separate module maths_path.py to hold the directory of the package. – nebffa Oct 16 '13 at 05:58

Unable to use __init__.py

2 Answers2

Unable to use init.py