Relative imports - ModuleNotFoundError: No module named x

Question

This is the first time I've really sat down and tried python 3, and seem to be failing miserably. I have the following two files:

1. test.py
2. config.py

config.py has a few functions defined in it as well as a few variables. I've stripped it down to the following:

config.py

debug = True

test.py

import config
print (config.debug)

I also have an __init__.py

However, I'm getting the following error:

ModuleNotFoundError: No module named 'config'

I'm aware that the py3 convention is to use absolute imports:

from . import config

However, this leads to the following error:

ImportError: cannot import name 'config'

So I'm at a loss as to what to do here... Any help is greatly appreciated. :)

Solution 1

As was stated in the comments to the original post, this seemed to be an issue with the python interpreter I was using for whatever reason, and not something wrong with the python scripts. I switched over from the WinPython bundle to the official python 3.6 from python.org and it worked just fine. thanks for the help everyone :)

Solution 2

TL;DR: You can't do relative imports from the file you execute since __main__ module is not a part of a package.

Absolute imports - import something available on sys.path

Relative imports - import something relative to the current module, must be a part of a package

If you're running both variants in exactly the same way, one of them should work. Here is an example that should help you understand what's going on. Let's add another main.py file with the overall directory structure like this:

.
./main.py
./ryan/__init__.py
./ryan/config.py
./ryan/test.py

And let's update test.py to see what's going on:

# config.py
debug = True

# test.py
print(__name__)

try:
    # Trying to find module in the parent package
    from . import config
    print(config.debug)
    del config
except ImportError:
    print('Relative import failed')

try:
    # Trying to find module on sys.path
    import config
    print(config.debug)
except ModuleNotFoundError:
    print('Absolute import failed')

# main.py
import ryan.test

Let's run test.py first:

$ python ryan/test.py
__main__
Relative import failed
True

Here "test" is the __main__ module and doesn't know anything about belonging to a package. However import config should work, since the ryan folder will be added to sys.path.

Let's run main.py instead:

$ python main.py
ryan.test
True
Absolute import failed

And here test is inside of the "ryan" package and can perform relative imports. import config fails since implicit relative imports are not allowed in Python 3.

Hope this helped.

P.S.: If you're sticking with Python 3 there is no more need for __init__.py files.

Solution 3

I figured it out. Very frustrating, especially coming from python2.

You have to add a . to the module, regardless of whether or not it is relative or absolute.

I created the directory setup as follows.

/main.py
--/lib
  --/__init__.py
  --/mody.py
  --/modx.py

modx.py

def does_something():
    return "I gave you this string."

mody.py

from modx import does_something

def loaded():
    string = does_something()
    print(string)

main.py

from lib import mody

mody.loaded()

when I execute main, this is what happens

$ python main.py
Traceback (most recent call last):
  File "main.py", line 2, in <module>
    from lib import mody
  File "/mnt/c/Users/Austin/Dropbox/Source/Python/virtualenviron/mock/package/lib/mody.py", line 1, in <module>
    from modx import does_something
ImportError: No module named 'modx'

I ran 2to3, and the core output was this

RefactoringTool: Refactored lib/mody.py
--- lib/mody.py (original)
+++ lib/mody.py (refactored)
@@ -1,4 +1,4 @@
-from modx import does_something
+from .modx import does_something

 def loaded():
     string = does_something()
RefactoringTool: Files that need to be modified:
RefactoringTool: lib/modx.py
RefactoringTool: lib/mody.py

I had to modify mody.py's import statement to fix it

try:
    from modx import does_something
except ImportError:
    from .modx import does_something


def loaded():
    string = does_something()
    print(string)

Then I ran main.py again and got the expected output

$ python main.py
I gave you this string.

Lastly, just to clean it up and make it portable between 2 and 3.

from __future__ import absolute_import
from .modx import does_something

Solution 4

You have to append your project's path to PYTHONPATH and make sure to use absolute imports.

---

For UNIX (Linux, OSX, ...)

export PYTHONPATH="${PYTHONPATH}:/path/to/your/project/"

For Windows

set PYTHONPATH=%PYTHONPATH%;C:\path\to\your\project\

---

Absolute imports

Assuming that we have the following project structure,

└── myproject
    ├── mypackage
    │   ├── __init__.py
    │   ├── a.py
    └── anotherpackage
        ├── __init__.py
        ├── b.py
        ├── c.py
        └── mysubpackage
            ├── __init__.py
            └── d.py

just make sure to reference each import starting from the project's root directory. For instance,

# in module a.py
import anotherpackage.mysubpackage.d

# in module b
import anotherpackage.c
import mypackage.a

---

For a more comprehensive explanation, refer to the article How to fix ModuleNotFoundError and ImportError

Solution 5

Setting PYTHONPATH can also help with this problem.

Here is how it can be done on Windows

set PYTHONPATH=.

View more solutions

Comments

[Copperfield]

I cannot reproduce the error, how do you execute this code?

[blitzmann]

I execute test.py through pyCharm with Python 3.6. Does yours execute fine?

[Copperfield]

I execute it with idle that come with python, and also as python test.py, and it work perfectly fine. I don't have pyCharm, but perhaps is some bad configuration of pyCharm that is causing the problem

[blitzmann]

Very odd. I'm using WinPython - just download vanilla Python 3.6 from python.org, and it works fine. Never thought to check the interpreter! Thanks!

[Martin Tournoij]

My guess is that something funky is going on with PYTHONPATH. Check your IDE settings and/or system environment variables.

[Admin]

I have this same exact problem. It is not pycharm! It is python3. It works in python2, but when using python3, you see this error! very frustrating.

[ParaH2]

sys.path.append(r'C:/.../LastFolder') works all the time

[mrgloom]

If I run it from console first option works for me and second gives me "ImportError: attempted relative import with no known parent package".

[naoko]

Hmm hate to say this but same thing just happened to me. Recreating environment fix the issue. In my case, I was getting this error when running tests. In the same environment, attempt to import same module worked. Recreating environment fixed them all (same python version 3.6)

[James T.]

Is there something I can do to make absolute imports always work? Like, call sys.path.append('/some/path/my_module') inside of /some/path/my_module/__init__.py ?

[Igonato]

@JamesT. Yes, it's pretty common to modify sys.path during runtime (github.com/…). You can also set PYTHONPATH environment variable.

[Geek]

setting PYTHONPATH to main code directory solved the problem for me!

[winux]

Different IDE's have different way of handling path's specially for project source files (views, modules, templates, etc.) If your project is structured and coded properly, then it should work to all (standard) IDE's. Having issues with popular IDE's like WinPython means the problem is indeed coming from your project. As mentioned above, the problem is "You have to add a . to the module" by user3159377 which should be the accepted answer.

[Kevin]

"if you're sticking with Python 3 there is no more need in __init__.py files." Interesting. Can you elaborate on this? I was under the impression that the package resolution mechanism hasn't changed all that much between 2 and 3.

[smci]

"if you're sticking with Python 3 there is no more need for __init__.py files." Conversely, can you describe things if we want a package to work in both 2 and 3? And see the woefully-out-of-date 2009 What is __init__.py for? and its most highly-upvoted answer "It's a part of a package". We need to start emphasizing the distinction "regular package [old, pre-3.3]" vs "namespace package [3.3+]" everywhere and often.

[Mayur]

This is what I was exactly looking for. Thanks for sharing this answer!!!

[Tony Fraser]

Huge thanks @Giorgos! This is especially true when you're trying to set a root directory in a docker image.

[Sharad]

Doing something like this gives a linter (pylint3) error. The error is similar to this one. filename.py:12:0: C0413: Import "import abc.def.ghi.file_util as file_util" should be placed at the top of the module (wrong-import-position)

[Justapigeon]

Worth noting that the try/except loading procedure is the real ingredient that works here (as some people will need to use try:scripts.modx and except: modx), and was what solved this issue for me.

[rjdkolb]

Works in Linux as well. export PYTHONPATH=.

[ingyhere]

Try/except on import is ugly. I wish there was a better solution.

[Giorgos Myrianthous]

You have to add a . to the module, regardless of whether or not it is relative or absolute This is not quite accurate. If you use the dot, then it becomes a relative import.

[BVengerov]

Sorry for spamming in the comment section, but... man, thanks so much for your answer @Igonato!

[VISQL]

Excellent. These contents for the __init__ file work in Python 3.6.6

[torez233]

thanks for the answer. I am wondering if in main.py, "from ryan import test" is equivalent to "import ryan.test" (ignore the namespace prefix differenence, i.e. in the former we can access via test while in the latter we have to access via ryan.test)? Are those two going to import the same set of variables defined in the namespace of test, and are they both absolute import?

[Aidos]

thank you so much! this dot (.) was the actual problem for me =)

[etoricky]

I am using a library called generateDS and I add a dot at the module name and solve the problem in 2021! Thanks!

[user7630232]

This worked like charm! thanks a lot.

[mrgloom]

What is "part of a package" here mean?

[mrgloom]

What is in the sys.path in this example?

[mrgloom]

Why we don't import it like "from ryan import config"?

[llincolnatal]

don't forget import sys :)

[Admin]

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

[altela]

adding . when importing a file (in my case, from .file1 import my_var) still working great in python 3.7, thank you

[Harshad Vyawahare]

Another version of the same answer, this also works: sys.path.append(os.path.join(os.path.dirname(__file__), os.pardir)) Here omitted a few things like: os.path.abspath or os.path.realpath