Python: importing a sub‑package or sub‑module

Question

Having already use flat packages, I was not expecting the issue I encountered with nested packages. Here is… Directory layout ``` dir | +-- test.py | +-- package | +-- __init__.py | +-- subpackage | +-- __init__.py | +-- module.py ``` Content of init.py Both `package/__init__.py` and `package/subpackage/__init__.py` are empty. Content of `module.py` ``` # file `package/subpackage/module.py` attribute1 = "value 1" attribute2 = "value 2" attribute3 = "value 3" # and as many more as you want... ``` Content of `test.py` (3 versions) Version 1 ``` # file test.py from package.subpackage.module import * print attribute1 # OK ``` That's the bad and unsafe way of importing things (import all in a bulk), but it works. Version 2 ``` # file test.py import package.subpackage.module from package.subpackage import module # Alternative from module import attribute1 ``` A safer way to import, item by item, but it fails, Python don't want this: fails with the message: "No module named module". However…

Accepted Answer

You seem to be misunderstanding how `import` searches for modules. When you use an import statement it always searches the actual module path (and/or `sys.modules`); it doesn't make use of module objects in the local namespace that exist because of previous imports. When you do:

```
import package.subpackage.module
from package.subpackage import module
from module import attribute1
```

The second line looks for a package called `package.subpackage` and imports `module` from that package. This line has no effect on the third line. The third line just looks for a module called `module` and doesn't find one. It doesn't "re-use" the object called `module` that you got from the line above.

In other words `from someModule import ...` doesn't mean "from the module called someModule that I imported earlier..." it means "from the module named someModule that you find on sys.path...". There is no way to "incrementally" build up a module's path by importing the packages that lead to it. You always have to refer to the entire module name when importing.

It's not clear what you're trying to achieve. If you only want to import the particular object attribute1, just do `from package.subpackage.module import attribute1` and be done with it. You need never worry about the long `package.subpackage.module` once you've imported the name you want from it.

If you do want to have access to the module to access other names later, then you can do `from package.subpackage import module` and, as you've seen you can then do `module.attribute1` and so on as much as you like.

If you want both --- that is, if you want `attribute1` directly accessible and you want `module` accessible, just do both of the above:

```
from package.subpackage import module
from package.subpackage.module import attribute1
attribute1 # works
module.someOtherAttribute # also works
```

If you don't like typing `package.subpackage` even twice, you can just manually create a local reference to attribute1:

```
from package.subpackage import module
attribute1 = module.attribute1
attribute1 # works
module.someOtherAttribute #also works
```

Python: importing a sub‑package or sub‑module

Solution

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