https://github.com/joaduo/rel_imp
Relative import tool for running subpackages or submodules as main scripts (enabling explicit relative imports)
https://github.com/joaduo/rel_imp
Last synced: 7 months ago
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Relative import tool for running subpackages or submodules as main scripts (enabling explicit relative imports)
- Host: GitHub
- URL: https://github.com/joaduo/rel_imp
- Owner: joaduo
- License: mit
- Created: 2014-09-05T23:41:32.000Z (almost 12 years ago)
- Default Branch: master
- Last Pushed: 2022-03-15T17:31:51.000Z (about 4 years ago)
- Last Synced: 2025-02-04T04:53:23.033Z (over 1 year ago)
- Language: Python
- Homepage:
- Size: 48.8 KB
- Stars: 1
- Watchers: 2
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# The rel_imp utility
[ ](https://codeship.com/projects/70108)
Enabling explicit relative imports in main modules the easy way.
For enabling relative import in `__main__` module PEP 366 presents a workaround like:
```python
if __name__ == "__main__" and __package__ is None:
__package__ = "my_pkg"
from .foo import bar
```
With `rel_imp` you can rewrite it as:
```python
import rel_imp; rel_imp.init()
from .foo import bar
```
Cleaner, faster and less coupled. (you don't need to specify the package manually)
**Note:** In order to use `rel_imp` the module you are coding must be inside a package or a sub-package.
## Why using explicit relative imports?
Python 2 still supports implicit relative import and will be deprecated in Python 3, so you will want to migrate those scripts using implicit relative import to explicit relative import. Check more on the [PEP 404](http://legacy.python.org/dev/peps/pep-0404/#id18).
Explicit relative imports makes your code less coupled. As [PEP 328](http://legacy.python.org/dev/peps/pep-0328/#rationale-for-relative-imports) says:
> Several use cases were presented, the most important of which is being able to rearrange the structure of large packages without having to edit sub-packages. In addition, a module inside a package can't easily import itself without relative imports.
On the other hand PEP 8 says:
> Absolute imports are recommended, as they are usually more readable and tend to be better behaved (or at least give better error messages) if the import system is incorrectly configured.
If you find a point to use explicit relative imports, then you can use rel_imp to allow running packages as main.
## Why running sub-modules as main?
Some reasons:
1. A submodule can become a command line tool if called as main.
2. You can have unit test or smoke test within the module.
3. You simply want to run it without any explicit test to see if at least it imports everything it needs.
## Installation and Uninstallation
### Install via pip
```
pip install rel_imp
```
Remove it with:
```
pip uninstall rel_imp
```
### Install downloading the file
Download the `rel_imp.py` in one your Python's search path.
```
wget https://raw.githubusercontent.com/joaduo/rel_imp/master/rel_imp.py
```
## Example
Imagine you have 2 modules inside a package called "my_pkg".
That would be:
* `my_pkg/__init__.py`
* `my_pkg/math_lib.py`
* `my_pkg/test.py`
So in test.py we could have
```python
from .math_lib import factorize
def factorize_and_print(number):
num = factorize(number)
print num
if __name__ == '__main__':
#Small smoke test
factorize_and_print(10)
factorize_and_print(0)
factorize_and_print(-10)
```
If you do `python my_pkg/test.py` it will throw an exception because of the relative import at the first line.
So you can use `rel_imp` to make your code look nicer. Simply do:
```python
import rel_imp; rel_imp.init()
from .math_lib import factorize
```
It is equivalent as the prior solution but you don't have to worry about keeping in sync `__package__`'s value.
You can also use a shorter solution with implicit `init()` using the `relative_import` module:
```python
import relative_import
from .math_lib import factorize
```
## How does it work?
It uses the same technique in PEP 366 but `__package__`'s value is set through dynamic inspection of the stack. To solve the value of `__package__` it compares the current `__main__`'s file with search paths in sys.path - or, optionally, a list of paths given in the settings -.
For example, for a file in `/home/user/projects/python/math/my_pkg/test.py` given the following paths in sys.path:
```python
[
'/home/user/projects/python/',
'/home/user/projects/python/math/',
'/home/user/projects/python/math/my_pkg/',
]
```
It will pick the closest path to the `__main__`'s file that is not the `__main__`'s file's directory.
Then the base path use to solve `__package__` variable will be `/home/user/projects/python/math/`
This process is only done once and for the `__main__`. Succesive calls to `rel_imp.init()` does nothing.
## Disabling `rel_imp` initialization
You can simply define a environment variable `PYTHON_DISABLE_REL_IMP` with any value.
## Feedback or bugs reporting
File an issue through github's [issue tracking system](https://github.com/joaduo/rel_imp/issues).
You can optionally contact me at joaduo gmail com.
## Related PEPs
* http://legacy.python.org/dev/peps/pep-0328/
* http://legacy.python.org/dev/peps/pep-0366/