How to fix "Attempted relative import in non-package" even with __init_

J

John Strood

To elaborate on Ignacio Vazquez-Abrams's answer:

The Python import mechanism works relative to the __name__ of the current file. When you execute a file directly, it doesn't have its usual name, but has "__main__" as its name instead. So relative imports don't work.

You can, as Igancio suggested, execute it using the -m option. If you have a part of your package that is meant to be run as a script, you can also use the __package__ attribute to tell that file what name it's supposed to have in the package hierarchy.

See http://www.python.org/dev/peps/pep-0366/ for details.

Took a while for me to realize you can't run python -m core_test from within the tests subdirectory - it has to be from the parent, or you have to add the parent to the path.

@DannyStaple: Not exactly. You can use __package__ to ensure executable script files can relatively import other modules from within the same package. There's no way to relatively import from "the whole system". I'm not even sure why you'd want to do this.

I mean if the __package__ symbol is set to "parent.child" then you'd be able to import "parent.other_child". Perhaps I didn't phrase it so well.

@DannyStaple: Well, how it works is described in the linked documentation. If you have a script script.py in package pack.subpack, then setting it's __package__ to pack.subpack will let you do from ..module import something to import something from pack.module. Note that, as the documentation says, you still have to have the top-level package on the system path. This is already the way things work for imported modules. The only thing __package__ does is let you use that behavior for directly-executed scripts as well.

I use __package__ in the script which is executed directly but Unfortunately, I get the the following error: "Parent module 'xxx' not loaded, cannot perform relative import"

I

Ignacio Vazquez-Abrams

Yes. You're not using it as a package.

python -m pkg.tests.core_test

A gotcha: Note that there is no '.py' at the end!

I'm not either of the downvoters, but I feel this could use quite a bit more detail, given the popularity of this question and answer. Noting stuff like from what directory to execute the above shell command, the fact that you need __init__.pys all the way down, and the __package__-modifying trickery (described below by BrenBarn) needed to allow these imports for executable scripts (e.g. when using a shebang and doing ./my_script.py at the Unix shell) would all be useful. This whole issue was quite tricky for me to figure out or find concise and understandable documentation on.

Note: you need to be outside of the directory pkg at the point where you call this line from the CLI. Then, it should work as expected. If you are inside pkg and you call python -m tests.core_test, it will not work. At least it didn't for me.

Seriously, can you explain whats going on in your answer?

@MarkAmery Almost lost my mind trying to grok how all this works, relative imports within a project with subdirectories with py files that have __init__.py files yet you keep getting the ValueError: Attempted relative import in non-package error. I would pay really good money for someone, somewhere, to finally explain in plain English how all of this works.

P

Paolo Rovelli

It depends on how you want to launch your script.

If you want to launch your UnitTest from the command line in a classic way, that is:

python tests/core_test.py

Then, since in this case 'components' and 'tests' are siblings folders, you can import the relative module either using the insert or the append method of the sys.path module. Something like:

import sys
from os import path
sys.path.append( path.dirname( path.dirname( path.abspath(__file__) ) ) )
from components.core import GameLoopEvents

Otherwise, you can launch your script with the '-m' argument (note that in this case, we are talking about a package, and thus you must not give the '.py' extension), that is:

python -m pkg.tests.core_test

In such a case, you can simply use the relative import as you were doing:

from ..components.core import GameLoopEvents

You can finally mix the two approaches, so that your script will work no matter how it is called. For example:

if __name__ == '__main__':
    if __package__ is None:
        import sys
        from os import path
        sys.path.append( path.dirname( path.dirname( path.abspath(__file__) ) ) )
        from components.core import GameLoopEvents
    else:
        from ..components.core import GameLoopEvents

what shall i do if i am trying to use the pdb for debugging? since you use python -m pdb myscript.py to launch the debugging session.

@dannynjust -- That's a good question since you can't have 2 main modules. Generally when debugging, I prefer to drop into the debugger manually at the first point where I want to start debugging. You can do that by inserting a import pdb; pdb.set_trace() into the code (inline).

Is it better to use insert instead of append? That is, sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

Using insert is a better match for the relative import semantics, where local package names take precedence over installed packages. Especially for tests, you usually want to test the local version, not the installed one (unless your test infrastructure installs the code under test, in which case relative imports are unneeded and you won't have this problem).

you should also mention that you can't be in the directory containing core_test when you run as a module (that would be too easy)

M

Miles Erickson

You can use import components.core directly if you append the current directory to sys.path:

if __name__ == '__main__' and __package__ is None:
    from os import sys, path
    sys.path.append(path.dirname(path.dirname(path.abspath(__file__))))

sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))) this will also work

from os import sys looks like cheating :)

@Piotr: It's might be considered better because it slightly shows more clearly what is being being appended to sys.path -- the parent of the directory the current file is in.

@flyingsheep: Agreed, I'd just use a regular import sys, os.path as path.

FYI, to use this in an ipython notebook, I adapted this answer to: import os; os.sys.path.append(os.path.dirname(os.path.abspath('.'))). Then a straight import components.core works for me, importing from the notebook's parent directory as desired.

A

Allan Mwesigwa

In core_test.py, do the following:

import sys
sys.path.append('../components')
from core import GameLoopEvents

d

deepak

If your use case is for running tests, and it seams that it is, then you can do the following. Instead of running your test script as python core_test.py use a testing framework such as pytest. Then on the command line you can enter

$$ py.test

That will run the tests in your directory. This gets around the issue of __name__ being __main__ that was pointed out by @BrenBarn. Next, put an empty __init__.py file into your test directory, this will make the test directory part of your package. Then you will be able to do

from ..components.core import GameLoopEvents

However, if you run your test script as a main program then things will fail once again. So just use the test runner. Maybe this also works with other test runners such as nosetests but i haven't checked it. Hope this helps.

M

Mohideen bin Mohammed

Issue is with your testing method,

you tried python core_test.py

then you will get this error ValueError: Attempted relative import in non-package

Reason: you are testing your packaging from non-package source.

so test your module from package source.

if this is your project structure,

pkg/
  __init__.py
  components/
    core.py
    __init__.py
  tests/
    core_test.py
    __init__.py

cd pkg

python -m tests.core_test # dont use .py

or from outside pkg/

python -m pkg.tests.core_test

single . if you want to import from folder in same directory . for each step back add one more.

hi/
  hello.py
how.py

in how.py

from .hi import hello

incase if you want to import how from hello.py

from .. import how

In the example from .. import how, how do you import a specific class / method from the 'how' file. when I do the equivalent of from ..how import foo then I get "attempted relative import beyond top-level package"

@JamesHulse Does from .. import how work but the second statement not? I would have assumed that both statements won't work, if the folder that contains the hi folder does not contain an _ _ init _ _.py file. In other words, if there is only an init file in the hi folder, then the hi folder is the top level package and you cannot address beyond it.

v

v4gil

My quick-fix is to add the directory to the path:

import sys
sys.path.insert(0, '../components/')

Your approach wont work in all cases because '../' part is resolved from directory from which you run your script(core_test.py). With your approach you are forced to cd to 'tests' before running the core_test.py scritp.

z

zhengcao

As Paolo said, we have 2 invocation methods:

1) python -m tests.core_test
2) python tests/core_test.py

One difference between them is sys.path[0] string. Since the interpret will search sys.path when doing import, we can do with tests/core_test.py:

if __name__ == '__main__':
    import sys
    from pathlib import Path
    sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
    from components import core
    <other stuff>

And more after this, we can run core_test.py with other methods:

cd tests
python core_test.py
python -m core_test
...

Note, py36 tested only.

J

John Difool

Old thread. I found out that adding an __all__= ['submodule', ...] to the __init__.py file and then using the from <CURRENT_MODULE> import * in the target works fine.

J

Jayhello

You can use from pkg.components.core import GameLoopEvents, for example I use pycharm, the below is my project structure image, I just import from the root package, then it works:

https://i.stack.imgur.com/O8dKL.png

This did not work for me. Did you have to set the path in your configuration?

@MohammadMahjoub You need all the init files that he also has to make this work... Don't forget the one in cnn_scratch

R

Rick Graves

This approach worked for me and is less cluttered than some solutions:

try:
  from ..components.core import GameLoopEvents
except ValueError:
  from components.core import GameLoopEvents

The parent directory is in my PYTHONPATH, and there are __init__.py files in the parent directory and this directory.

The above always worked in python 2, but python 3 sometimes hit an ImportError or ModuleNotFoundError (the latter is new in python 3.6 and a subclass of ImportError), so the following tweak works for me in both python 2 and 3:

try:
  from ..components.core import GameLoopEvents
except ( ValueError, ImportError):
  from components.core import GameLoopEvents

V

Vaishnavi Bala

Try this

import components
from components import *

s

suriyanto

As you have already marked everything as a module, there's no need to use the relative reference if you launch as python module.

Instead of

from ..components.core import GameLoopEvents

simply

from pkg.components.core import GameLoopEvents

When you run from the parent of pkg, use the following

python -m pkg.tests.core_test

H

HappyWaters

If someone is looking for a workaround, I stumbled upon one. Here's a bit of context. I wanted to test out one of the methods I've in a file. When I run it from within

if __name__ == "__main__":

it always complained of the relative imports. I tried to apply the above solutions, but failed to work, since there were many nested files, each with multiple imports.

Here's what I did. I just created a launcher, an external program that would import necessary methods and call them. Though, not a great solution, it works.

S

SteveCalifornia

Here's one way which will piss off everyone but work pretty well. In tests run:

ln -s ../components components

Then just import components like you normally would.

This is a seriously undervalued gem! I can't understand why there are not enough up-votes to make this answer near the top!

K

Kai Aeberli

For me only this worked: I had to explicitly set the value of package to the parent directory, and add the parent directory to sys.path

from os import path
import sys
if __package__ is None:
    sys.path.append( path.dirname( path.dirname( path.abspath(__file__) ) ) )
    __package__= "myparent"

from .subdir import something # the . can now be resolved

I can now directly run my script with python myscript.py.

m

mon

python

.py does not work with relative import

The problem is relative import does not work when you run a __main__ module from the command line

python <main_module>.py

It is clearly stated in PEP 338.

The release of 2.5b1 showed a surprising (although obvious in retrospect) interaction between this PEP and PEP 328 - explicit relative imports don't work from a main module. This is due to the fact that relative imports rely on __name__ to determine the current module's position in the package hierarchy. In a main module, the value of __name__ is always '__main__', so explicit relative imports will always fail (as they only work for a module inside a package).

Cause

Python Bug Tracker Issue1510172: Absolute/relative import not working?

The issue isn't actually unique to the -m switch. The problem is that relative imports are based on __name__, and in the main module, __name__ always has the value __main__. Hence, relative imports currently can't work properly from the main module of an application, because the main module doesn't know where it really fits in the Python module namespace (this is at least fixable in theory for the main modules executed through the -m switch, but directly executed files and the interactive interpreter are completely out of luck).

To understand further, see Relative imports in Python 3 for the detailed explanation and how to get it over.

S

SANTI SANTOSH MAHAPATRA

This is very confusing, and if you are using IDE like pycharm, it's little more confusing. What worked for me: 1. Make pycharm project settings (if you are running python from a VE or from python directory) 2. There is no wrong the way you defined. sometime it works with from folder1.file1 import class

if it does not work, use import folder1.file1 3. Your environment variable should be correctly mentioned in system or provide it in your command line argument.

R

Ronny

I've had similar issues and as a software engineer, I think some of the suggested solutions here are not ideal. If you want relative imports, you should not have try/except and then sometimes do an absolute import. Also, to run a program, you should not have to change sys.path.

Furthermore, the program should always work, independent of your current working directory and independent of how you start it.

Thus, I've created a new, experimental import library: ultraimport It allows file system based imports, no matter how you run your code.

From the original question, you would change your core_test.py to something like

import ultraimport
GameLoopEvents = ultraimport('__dir__/../components/core.py', 'GameLoopEvents')
print(GameLoopEvents)

and it would always find it, no matter how you run your tests.

$ python -m tests.core_test
<class 'core.GameLoopEvents'>
 python ./tests/core_test.py 
<class 'core.GameLoopEvents'>

I've also put this example into the examples folder in the git repo.

As the library is experimental, I am interested in feedback. It works for me but it not widely tested, yet.

r

rosefun

Because your code contains if __name__ == "__main__", which doesn't be imported as a package, you'd better use sys.path.append() to solve the problem.

I don't think having if __name__ == "__main__" in your file makes a difference to anything related to importing.

How to fix "Attempted relative import in non-package" even with init.py

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How to fix "Attempted relative import in non-package" even with __init__.py