Develop Reference

How to import a class located in another root directory folder

Using Python 3.7.9 and having a file directory hierarchy like this
Application
| |
| └── __init__.py
|
├── CLS
│ └── Article.py
│ └── __init__.py
│
└── OUT
└── publish.py
└── __init__.py
As you can see I have the __init__.py located in all folders Application, CLS, and OUT now when I am trying to import the Article.py file (which contains a Python class definition) into publish.py like
from Application.CLS.Article import Article
or
from CLS.Article import Article
or
from ...CLS.Article import Article
I am getting this error message
ModuleNotFoundError Traceback (most recent call last)
<ipython-input-9-8542540653f1> in <module>
----> 1 from Application.CLS.Article import Article
ModuleNotFoundError: No module named 'Application.CLS.Article'; 'CLS.Article' is not a package
Why is this still happening while I have the __init__.py located in all folder levels?

It looks like you have not set the PYTHONPATH environment variable.
If you are on linux, you can cd to the directory where you are executing your code from and run
export PYTHONPATH="$pwd"
This is a temporary fix, you will need to run this every time you open a new terminal session.
For a more permanent solution, you can hardcode the location to your code directory in your .bashrc file.
Or if you are on a different OS check the following link:
PYTHONPATH
And if you are on Windows specifically:
PYTHONPATH in Windows

Module import from own directory not found. How to fix it?

A get an error when trying to run my code but somehow vs code doesn't see the path error.
The error:
ModuleNotFoundError: No module named 'get_formats'
The structure of my code is:
application
├── data_processor
│ ├── extract_movements.py
│ └── get_formats
│ └── get_formats.py
├── get_user_input
│ ├── get_bank_name.py
│ └── get_pdf_name.py
└── operate.py
And the error occures in extract_movements.py where I am trying to import a funtion located in get_formats.py using:
from get_formats.get_formats import get_transaction_tags_format, get_transaction_dates_format
The complete error shown is:
Traceback (most recent call last):
File "/Users/username/Desktop/application/operate.py", line 6, in <module>
from data_processor.extract_movements import extract_movements
File "/Users/username/Desktop/application/data_processor/extract_movements.py", line 1, in <module>
from get_formats.get_formats import get_transaction_tags_format, get_transaction_dates_format
ModuleNotFoundError: No module named 'get_formats'
I see some answers talk about an __init__.py file in the application directory or the data_processor directory so i tried adding that but got no results. Also have no idea what an empty file with the name __init__.py

If you make an __init__.py script in your directory, you'll be able to access sibling files.
Why wasn't your __init__.py working? - You need an __init__.py inside the get_formats directory not outside, otherwise that directory will not be treated as a module.
However the easiest option is to use the sys module, like sys.path.append in the second answer here Importing files from different folder , or like this: How to import .py file from another directory?

ModuleNotFound: No module named 'module_name'

My project structure is the following:
.
└── project name
├── project name
│ ├── __init__.py
│ ├── module.py
│
├── PACKAGE_A
│ ├── __init__.py
│ ├── PACKAGE_A.py
│ ├── module_a.py
│
In PACKAGE_A.py
from module_a import Some_Class
a = Some_Class()
class Another_Class:
# class code here
In module.py
"""
Notes
-----
https://stackoverflow.com/questions/16780014/import-file-from-parent-directory
"""
# Standard library imports
import os, sys
sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
# Local application imports
from PACKAGE_A.PACKAGE_A import Another_Class
from PACKAGE_A.module_a import some_function
While module_a.py and PACKAGE_A.py run without problem, running module.py fails with:
Traceback (most recent call last):
File "path\to\project name\project name\module.py", line 12, in <module>
from PACKAGE_A.PACKAGE_A import Another_Class
File "path\to\project name\PACKAGE_A\PACKAGE_A.py", line 1, in <module>
from module_a import Some_Class
ModuleNotFoundError: No module named 'module_a'
What am I doing wrong here?

You need to change your import statement in PACKAGE_A.py from:
from module_a import Some_Class
to:
from PACKAGE_A.module_a import Some_Class
The reason is that you are adding the path\to\project name\ to sys.path, but you have no module_a.py in path\to\project name\, and path\to\project name\PACKAGE_A (where module_a.py resides) is not in sys.path.
As for why you succeed in running everything in PACKAGE_A, it's because Python adds the directory containing the script you are running to the list (as explained by gaFF).
I would recommend you read a bit more about python imports, if the doc seems too cluttered, you can check this link.
This is a personal preference, but I find it simpler to add the root directory of the project to the PYTHONPATH environment variable and then running all the scripts from that directory's level and changing the import statements accordingly. In your example, the root directory would be path\to\project name\.

import search for your packages in specific places, listed in sys.path. See the doc for the full details.
The current directory is always appended to this list, that's why you succeed to run everything inside PACKAGE_A. But from project name, there is no way to know where to find PACKAGE_A.
Solutions include:
use relative import
always run from the root directory (and start all your imports from the root directory)
add the root directory to the environment variable PYTHONPATH (same)
use a tool which sets PYTHONPATH when you enter your virtual environment (same)
...
and depends on your project and your needs.

ModuleNotFoundError while importing from different folder (Python)

I am having the age old problem of Module not found while importing files from different folder, kindly help me.
My project directory has the following things:
knowledge_generators --> __init__.py
knowledge_generator.py
absorb.py
In __init__.py I have the following content:
from knowledge_generator import *
And absorb.py has:
from knowledge_generators import *
On running absorb.py I get the following error:
File "D:/some/path/project/absorb.py", line 2, in <module>
from knowledge_generators import *
File "D:\some\path\project\knowledge_generators\__init__.py", line 1, in <module>
from knowledge_generator import *
ModuleNotFoundError: No module named 'knowledge_generator'
Also, on running __init__.py everything's working fine(i.e no ModuleNotFoundError). Kindly help me decipher the problem.

I suspect you need to use a relative import:
In __init__.py:
from .knowledge_generator import *

Working solution:
Just add your project root directory to environment variable: PYTHONPATH.
so for the below project structure, just add Rootdir path(For e.g: add E:\Projects\Rootdir) in PYTHONPATH.
Rootdir
└── pkg2
├── b.py
├── c.py
└── pkg2
├── b.py
├── c.py

Python "ImportError: No module named...", but the module exists

My file directory tree looks like this:
my_repo
├── experiments
│   ├── foo.py
│   └── __init__.py
└── tests
├── baz.py
└── __init__.py
Inside baz.py, I try
from experiments.foo import FooExperiment
but I get
*** ImportError: No module named experiments.foo
When I open python from the terminal (Mac OSX 10.9) and run
from experiments.foo import FooExperiment
the class is imported properly. What is going on? Please help.
In both situations the sys.path is exactly the same, except when I'm in baz.py the current path (to baz.py) is included. And yes /path/to/my_repo is in my sys.path as well.
EDIT: my issue was with conflicting egg files, so reinstalling did the trick (below). Accepting #Austin Marshall's answer though because it's a viable solution to the general case of this problem.
pip uninstall my_repo
python setup.py develop --user

experiments is not in PYTHONPATH, nor is it installed using the standard setuptools technique. I'm able to replicate your problem, which is resolved by putting my_repo in PYTHONPATH:
Austins-MacBook-Pro-2:my_repo amarshall$ tree .
.
├── experiments
│   ├── __init__.py
│   └── foo.py
└── tests
├── __init__.py
└── baz.py
2 directories, 4 files
Austins-MacBook-Pro-2:my_repo amarshall$ PATH=$PATH:`pwd`/experiments python tests/baz.py
Traceback (most recent call last):
File "tests/baz.py", line 1, in <module>
from experiments.foo import FooExperiment
ImportError: No module named experiments.foo
Austins-MacBook-Pro-2:my_repo amarshall$ PYTHONPATH=$PYTHONPATH:`pwd` python tests/baz.py
Where there's no output, or error in the last line when PYTHONPATH is specified, rather than PATH

I usually use the following to append path to sys.path:
sys.path.append(os.path.join(os.path.dirname(__file__), "../myfolder"))
With
Import sys, os