ultraimport 0.0.4

Reliable, file system based imports -- no matter how you run your code

ultraimport

Reliable, file system based imports -- no matter how you run your code.

Features:

• import any file from the file system as Python code
• forget about packages and modules, it's just a file and you can import it!
• preprocess code for optimizations
• recursively rewrite subsequent import statements
• re-import the same file as often as you want
• lazy loading (lazy imports for modules and callables)
• fix circular imports through lazy imports
• fix the error: ImportError: attempted relative import with no known parent package
• fix the error: ValueError: attempted relative import beyond top-level package

Warning: This is an early hack. No unit tests exist. Maybe not stable!

Is ultraimport supposed to replace the normal import statement?

No, not for now. The normal import statement will continue to exist to import 3rd party libraries. ultraimport is meant to import files whose locations you control because they are located relatively to some other files.

Installation

Install system wide:

pip install ultraimport

Install a local development version:

git clone https://github.com/ronny-rentner/ultraimport.git
pip install -e ./ultraimport

How To Use?

Note: You can find this and other examples in the examples folder.

Let's assume your new program in the folder ~/myprogram looks like this:

__init__.py
cache.py
log.py
run.py

run.py:

#!/usr/bin/env python3

# ultraimport needs to be installed and imported in the classical way.
import ultraimport

# Import the 'logger' object from 'log.py' that is located in the same
# directory as this file and add 'logger' to the global namespace.
# `__dir__` refers to the directory where run.py is in.
ultraimport('__dir__/log.py', 'logger', globals=globals())

# Lazy import the cache module. On the first access to any attribute of
# cache, the real cache module will be loaded
cache = ultraimport('__dir__/cache.py', lazy=True)

def main():
    # do something

    logger('I did something')

    cache.store('Something')

if __name__ == '__main__':
    main()
else:
    logger('I was imported')

With ultraimport, no matter how you call run.py, it will always find log.py.

The Python Import Issue

Classically, to do a relative import, your run.py would look like this:

#!/usr/bin/env python3

from .log import logger

def main():
    # do something

    logger('I did something')

if __name__ == 'main':
    main()

If you try to run the program in usual way, you'll get an error message:

$ python ./run.py
Traceback (most recent call last):
  File "/home/user/myprogram/./run.py", line 1, in <module>
    from .log import logger
ImportError: attempted relative import with no known parent package

Python programs or scripts can be executed in a number of different ways:

# Broken
python ~/myprogram/run.py

# Works
cd ~
python -c 'import myprogram.run'

# Works
python -m myprogram.run

# Broken
cd ~/myprogram
python -c 'import run'

# Broken
python -m run

# Broken
python ./run.py

# Broken
~/myprogram/run.py

The error ImportError: attempted relative import with no known parent package is rather erratic because the code has never changed.

There actually is a known parent package. It's the directory where the code lives in. Sometimes Python can see it, sometimes not.

Even if there was no parent package, what's the issue with importing a module that I only know from its relative position to my current module?

The Solution: ultraimport

With ultraimport your program run.py will always find log.py, no matter how you run it.

run.py:

#!/usr/bin/env python3

# ultraimport needs to be installed and imported in the classical way.
import ultraimport

# Import the 'logger' object from 'log.py' that is located in the same
# directory as this file and add 'logger' to the global namespace.
# `__dir__` refers to the directory where run.py is in.
ultraimport('__dir__/log.py', 'logger', globals=globals())

# Lazy import the cache module. On the first access to any attribute of
# cache, the real cache module will be loaded
cache = ultraimport('__dir__/cache.py', lazy=True)

def main():
    # do something

    logger('I did something')

    cache.store('Something')

if __name__ == '__main__':
    main()
else:
    logger('I was imported')

As you can see, you'll have to import ultraimport in the classical way. It's intended to be installed as a system-wide library. Afterwards, you can import your own code based on relative or absolute file system paths so it can always be found.

With ultraimport, Python code can be executed in an way and the imports keep working:

# Works
python ~/myprogram/run.py

# Works
cd ~
python -c 'import myprogram.run'

# Works
python -m myprogram.run

# Works
cd ~/myprogram
python -c 'import run'

# Works
python -m run

# Works
python ./run.py

# Works
~/myprogram/run.py

Parameters

def ultraimport(file_path, objects_to_import = None, globals=None, preprocessor=None, package=None, caller=None, use_cache=True, lazy=False)

file_path: path to a file to import, ie. 'my_lib.py'. It can have any file extension. Please be aware that you must provide the file extension. The path can be relative or absolute. You can use the special string __dir__ to refer to the directory of the caller which will be derived via inspetions. If you use advanced debugging tools (or want to save some CPU cycles) you might want to set caller=__file__.

objects_to_import: provide name of single object or the value '*' or an iterable of object names to import from file_path. If lazy=True, this should be a dict where the values declare the types of the imported objects.

globals: add the objects_to_import to the dict provided. Usually called with gloabls=globals() if you want the imported module to be added to the globals of the caller.

preprocessor: callable that takes the source code as an argument and that can return a modified version of the source code. Check out the debug-transform example on how to use the preprocessor.

package: can have several modes depending on if you provide a string or an int. If you provide a string, this string will be used as a value of the __package__ variable of the imported module. If you set an int, it means the number of directories to extract from the file_path to calculate the value of __package__. Usually you do not have to set this. It can only help in a few cases with nested relative imports when not using the resurse=True mode. If package is set to None, the module will be imported without setting a __package__.

use_cache: if set to False, allow re-importing of the same source file even if it was imported before.

lazy: if set to True and if objects_to_import is set to None, it will lazy import the module. If set to True and objects_to_import is a dict, the values of the dict must be the type of the object to lazy import from the module. Currently only the type callable is supported.

recurse: if set to True, a built-in preprocessor is activated to transparently rewrite all from .. import .. statements (only relative imports) to ultraimport() calls. Use this mode if you have no control over the source code of the impored modules.

Contributing

We love contributions!

ultraimport is open source, built on open source, and we'd love to have you hang out in our community.