Python: Import function from file whose name is a variable

Question

I have a file ./model_scripts/medians.py containing a function predict_volume(). [Output of tree in the bash terminal given below]

 model_scripts
 ├── __init__.py
 ├── medians.py
 └── ...

I need to import this function into another python script where the name of the python script from which the function must be imported (i.e. medians.py) is in the form of a string variable. The code I have written is:

model_name = 'medians'
...
model = getattr(__import__('model_scripts'), model_name)
vol = model.predict_volume()

But I get the following error at the first line:

AttributeError: 'module' object has no attribute 'medians'

Upon reading other answers (here), I added a __init__.py to the model_scripts directory. But I am still getting the above error.

This answer suggested using importlib:

import importlib
model_name = 'medians'
...
model = importlib.import_module('model_scripts.'+model_name)
vol = model.predict_volume()

Would appreciate any insights on why the first approach does not work but the second does.

The first is equivalent to from model_scripts import medians and the second is equivalent to import model_scripts.medians, which are two different requests. — cdhowie
– cdhowie, Commented Mar 7, 2017 at 19:38
@cdhowie: Isn't what I'm doing by typing ` model = getattr(__import__('model_scripts'), model_name)` the same as model = model_scripts.medians? — IM94
– IM94, Commented Mar 7, 2017 at 19:40
It should be. This assumes that model_scripts even exports medians. Does from model_scripts import medians work the way you think it should? — cdhowie
– cdhowie, Commented Mar 7, 2017 at 20:00
@cdhowie: Yes, it works as expected. However, if the module name 'medians' is a string variable, I cannot import it that way. — IM94
– IM94, Commented Mar 8, 2017 at 7:27

Community · Accepted Answer · 2017-05-23 12:10:52Z

3

The correct syntax for __import__ here is using fromlist along with it.

The following works (read here):

model = getattr(__import__('model_scripts', fromlist=[model_name]), model_name)

edited May 23, 2017 at 12:10

CommunityBot

11 silver badge

answered Mar 8, 2017 at 9:04

Shashank Dixena

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