ImportError: attempted relative import with no known parent package - GeekFomo

Hey there, Python explorer! Ever found yourself tangled up in the maze of relative imports? They can be a bit of a puzzle, right? Maybe you’ve bumped into an exception that left you puzzled – indeed, we’re talking about the notorious ImportError: attempted relative import with no known parent package.

You’ve stumbled upon a puzzle that can leave both Python newcomers and seasoned pros scratching their heads. But guess what? There’s absolutely no need to fret or let this little hiccup scare you off.

In this guide, we’re going to demystify this exception, explore what’s really going on behind the curtain, and most importantly, equip you with the know-how to tackle it like a pro. So, are you ready to turn this brain-teaser into a walk in the park? Without further ado, let’s jump right in and start untangling!

TL;DR For “ImportError: attempted relative import…”

This guide might be a bit lengthy, so here’s the TL;DR for you. Just a heads up, if you attempt a relative import in a module that isn’t part of a package, you’ll encounter an “ImportError: attempted relative import with no known parent package” exception. Keep that in mind!

In the remaining sections of this guide, we will go into greater detail about this rule of thumb. We’ll explore its origins, its applications, and why it’s regarded as a reliable guideline. This thorough examination will help you understand not only the ‘what’ but also the ‘why’ and ‘how’ behind this rule, enabling you to apply it more effectively in your own scenarios.

How relative imports are resolved in python?

To get a handle on this pesky “ImportError: attempted relative import with no known parent package” error, let’s take a fun journey into the world of Python’s relative imports. You’ll find the key to this puzzle in an exciting document called PEP 328, also known as “Imports: Multi-Line and Absolute/Relative.”

PEP 328 is like a treasure map for us because it’s where the idea of relative imports in Python was first introduced. This concept is super important when it comes to figuring out the magic behind how Python’s interpreter resolve relative imports. By digging into this, we’ll get to unravel the mysteries of Python’s import handling and get a deep dive into how the interpreter picks the right path when it encounters relative import. Exciting stuff, right?

So, Let’s take a friendly journey to PEP 328 and discover some cool insights on how Python stepped up its game by adding support for relative imports.

Relative imports use a module’s __name__ attribute to determine that module’s position in the package hierarchy.
PEP 328 -Imports: Multi-Line and Absolute/Relative

The idea we’re chatting about suggests that a relative import is, well, relative to the current package. Now, you might be asking yourself, “What do you mean by the current package?” Let me clear that up for you. Basically, the current package is the one that the current module is part of or operates within. However, it’s good to remember that not all modules are part of a package. So, for a relative import to work, the module where we’re trying the relative import needs to be part of a package. If it’s not, the Python interpreter will quickly let you know something’s not quite right.

Also, this idea is a neat roadmap for the Python interpreter when it’s working hard to find the current package. If the interpreter needs to import a module, it figures out where it is by sneakily checking out the __name__ variable. This variable clearly tells the interpreter what module it’s dealing with at the moment. This __name__ variable is like a trusty compass for the Python interpreter on its adventure of importing modules.

You might be wondering, “What should the Python interpreter do when the module’s name doesn’t contain any package information?” Well, don’t worry, PEP 328 has also got this covered!

If the module’s name does not contain any package information (e.g., it is set to __main__), then relative imports are resolved as if the module were a top-level module, regardless of where the module is actually located on the file system.
PEP 328 -Imports: Multi-Line and Absolute/Relative

Alright, let’s break this down – The __name__ variable, if it’s lacking any package information, is seen by the python interpreter as a top-level module (think of it as a module that’s not part of any package). In this scenario, the current package is non-existent. As a result, the python interpreter can’t pinpoint the location of the module you’re trying to import, and you end up with an ImportError: attempted relative import with no known parent package.

A perfect example of a module that doesn’t belong to any package is the __main__ module. This is the module you kick-start the python interrupter with, and it’s not part of any package. We’ll circle back to this example when we discuss how to avoid that pesky exception later

How to avoid “ImportError: attempted relative import…”

So you encountered the daunting ImportError: attempted relative import with no known parent package error message. As we see, this typically comes up when you try to do a relative import in a module that isn’t part of a package. Although it might seem like a complex issue, rest assured, it’s not as intimidating as it sounds, and we’re here to help you navigate it!

The crucial point to remember here is that for relative imports to function correctly, your module must be part of a package. If it’s not, this error will pop up, and you’ll be left scratching your head. However, once you understand this fundamental concept, you can start to take steps to ensure that your module is correctly set up.

You might now be wondering (and rightly so), how can you verify if a module is part of a package? Well, that’s an excellent question with a couple of straightforward answers!

One simple way to verify is to inspect the value of the name variable. If __name__ contains a dot (.), then guess what? You’re in luck! This dot signifies that your module is part of a package, and that’s great news.

Apart from the __name__ variable, another helpful method to determine if your module is part of a package is to check the value of the __package__ variable. If __package__ doesn’t equal None, then you’ve hit the jackpot! This means that your module is indeed part of a package, and you are on the right track.

So, the next time you come across that ImportError: attempted relative import with no known parent package error, keep calm, and check your __name__ and __package__ variables. Remember, as long as your module is part of a package, you’re good to go!

How to resolve “ImportError: attempted relative import…”

Having acquired the necessary knowledge on how to prevent this kind of error from occurring, it becomes equally important to understand how to tackle and resolve this error when it does occur.

In this regard, I will introduce three potential solutions. These solutions are designed to address this error in a way that is most effective and efficient. We will delve into each solution, exploring their specific steps and processes. After introducing these solutions, I will engage in a discussion with you, providing insight and guidance on which solution would be the most appropriate to use in your specific circumstances. Our goal is to equip you with the tools and knowledge you need to comfortably and confidently handle this error should it arise.

Sample for “ImportError: attempted relative import…”

Before we proceed further, let’s first work on drafting a script. The purpose of this script will be such that when it is invoked or called upon during the execution of our program, it will intentionally trigger this particular error that we are currently dealing with.

Suppose you have a project with the following simple directory structure:

 root
 ├── config.py
 └── package
     ├── __init__.py
     └── program.py

You are currently attempting to access variables that are defined in a file named config.py from within another file which is named program.py. At first glance, this might seem to be a rather straightforward task. As such, you have opted to make use of a method known as relative import in order to achieve this goal.

# root/config.py
count = 5

# root/package/program.py
from .. import config
print("config.count => {0}".format(config.count))

However, when invoking program.py script, An exception is raised :

$ python3 root/program.py
Traceback (most recent call last):
  File "/Users/kobi/root/package/main.py", line 2, in <module>
    from .. import config
ImportError: attempted relative import with no known parent package

In order to gain a deeper understanding of the program’s functionality, let’s take some time to review the values assigned to the __name__ and __package__ variables. We can do this by inserting log messages at the beginning of the modules mentioned above. This will allow us to track the flow of data and the behavior of these specific variables throughout the execution of the program, providing us with valuable insights

# root/config.py
print('__file__={0:<35} | __name__={1:<25} | __package__={2:<25}'.format(__file__,__name__,str(__package__)))

count = 5

# root/package/program.py
print('__file__={0:<35} | __name__={1:<25} | __package__={2:<25}'.format(__file__,__name__,str(__package__)))

from .. import config
print("config.count => {0}".format(config.count))

Now, let’s invoke again

$ python3 package/program.py
__file__=/Users/kobi/root/package/main.py | __name__=__main__                  | __package__=None                     
Traceback (most recent call last):
  File "/Users/kobi/projects/geekfomo/s1/root/package/main.py", line 4, in <module>
    from .. import config
ImportError: attempted relative import with no known parent package

Looking at the output above, you’ll notice that __package__ is set to None, while __name__ is set to __main__. These values might seem a little puzzling at first, but they’re actually pretty important for understanding our module’s context.

When __package__ is None, it’s like our module is telling us, “Hey, I’m not part of a package.” We can double-check this with __name__, which doesn’t have any dot notation, hinting that our module is going solo, not part of a larger package.

When Python sees this, it throws an exception. It can be a little confusing if you’re not familiar with these variable. That’s why understanding these values is so crucial. They give us a glimpse into our module’s world and alert us to any potential hiccups, like the exception we see here. Now, we can see how can we fix the issue.

Solution 1 : Change Directory Structure

Let’s make some tweaks to our directory and whip up a new script.

To start, we’re going to create a shiny new directory named new_root and move the root directory right into new_root.
Next up, we’ll create main.py in our new_root directory.
Lastly, we’re going to create a fresh, empty __init__.py inside the root directory. This is our way of telling the python interrupter that this directory is a package.

 new_root
 ├── main.py
 └── root
     ├── __init__.py
     ├── config.py
     └── package
         ├── __init__.py
         └── program.py

# main.py
print('__file__={0:<35} | __name__={1:<25} | __package__={2:<25}'.format(__file__,__name__,str(__package__)))

import root.package.program

$ python3 main.py
__file__=/Users/kobi/new_root/main.py | __name__=__main__                  | __package__=None                     
__file__=/Users/kobi/new_root/root/package/program.py | __name__=root.package.program      | __package__=root.package             
__file__=/Users/kobi/new_root/root/config.py | __name__=root.config               | __package__=root                     
config.count => 5

Great news, it works! Let’s dive into why. The module root.package.program is a part of root.package. You can see this in the second line (The print from the top of new_root/root/package/program.py).

And Here’s the best part. When this module is part of a package, the Python interpreter has all the info it needs to resolve the relative import in root/package/program.py successfully. Isn’t that cool?

Solution 2 : Use the -m option

In our first approach, we’ll need to whip up a new script. But don’t worry, in this solution, we’re going to use the -m option and skip the whole new script creation part.

Let’s jump right in and shuffle our directory structure around a bit to use the -m option:

First off, let’s create a shiny new directory named new_root and shift the root directory right into new_root.
Next, we’ll create a crisp, new, empty __init__.py inside the root directory. This is like sending a signal to the python interpreter that this directory is a package.

 new_root  
 └── root
     ├── __init__.py
     ├── config.py
     └── package
         ├── __init__.py
         └── program.py

In our current process, we’re going to be using python with the -m option and supplying it with the module root.package.program. This is a super important piece of the puzzle.

The python -m option is a handy tool that lets us locate and execute modules as scripts using the Python module namespace. Cool, right? But wait, there’s more! This option also sets the package information, as you’ll see in the output we’re about to look at. This is a bonus because it takes care of this part all on its own, making our task that much smoother and more efficient.

$ python3 -m root.package.program
__file__=/Users/kobi/new_root/root/program.py | __name__=__main__                  | __package__=root.package
__file__=/Users/kobi/new_root/root/config.py          | __name__=root.config               | __package__=root
config.count => 5

And guess what? It works! Let’s dive into why. So, the module root.package.program is part of root.package. You can see this right at the start (it’s printed from the top of new_root/root/package/program.py). When this module is part of a package, the python interpreter knows everything it needs to sort out the relative import in root/package/program.py successfully.

A quick note: Unlike PEP 328, when finding the package information, the python interpreter uses the value of __package__ , not relying on the value of __name__.

Solution 3 : Workaround Without Changing Directory Structure

In previous solutions, we’ve had to shake up the directory structure a bit. However, there are times when you’d rather keep that structure just the way it is. Maybe it’s because your code’s framework (django, pytest, airflow, fastapi, flask, you name it) or your working environment (pycharm, vscode, and jupyter notebook, for instance) leans heavily on that structure. In those instances, here’s a workaround you might find handy.

As we’ve seen in solution 2, our Python interpreter doesn’t work without the __package__ variable. This little variable is what it uses to figure out all the package info. So, when the __package__ is missing, our interpreter throws a fit, telling us we’ve done something wrong.

So, let’s use this insight to our advantage. We’ll wrap our relative import in an if statement, with the condition based on the value of the __package__ variable.

if __package__:
    from .. import config
else:
    sys.path.append(os.dirname(__file__) + '/..')
    import config

$ python3 root/package/program.py
__file__=/Users/kobi/root/package/main.py | __name__=__main__                  | __package__=None 
__file__=/Users/kobi/new_root/root/config.py          | __name__=config               | __package__=None
config.count => 5

It works! Want to know why? Well, if the __package__ isn’t None, we’re all set to use relative import. But, what if the __package__ is None? Uh-oh, relative import is out of the question then. But hey, don’t sweat it! We can simply add the module’s directory to sys.path and import the module we need. You see, sys.path is this really cool list of paths that helps our Python interpreter know exactly where to find our imported modules. So, our Python interpreter will just find the module we need. Pretty simple, isn’t it?

Just a heads up, this method can be a bit tricky. If a module with the same name (like our friend “config”) already exists somewhere in the sys path, the python interpreter might get a bit confused and import that one instead of ours. It’s like a surprise party, but with more bugs and a bit of mystery!

So use this workaround with caution and only when necessary.

The final thing we’re going to chat about is generating the directory. But don’t sweat it, I’m here to help! Firstly, all you’ve got to do is switch out the first dot in the relative import with os.dirname(file). Piece of cake, right? Then, for each dot that follows, just swap it with “../”. And to wrap it all up, just add on each piece between the dots. You’re doing great!

Let’s see some examples:

from . import config	sys.path.append( os.dirname(__file__) ) import config
from .. import config	sys.path.append( os.path.join( os.dirname(__file__), ‘..’ ) ) import config
from … import config	sys.path.append( os.path.join( os.dirname(__file__), ‘..’ , ‘..’ )) import config
from ..a.b.c import config	sys.path.append( os.path.join( os.dirname(__file__), ‘..’ , ‘a’ ,’b’ ,’c’ )) import config OR better (less chance for name clashing) sys.path.append( os.path.join( os.dirname(__file__), ‘..’ )) from a.b.c import config

Which solution should I use?

Alrighty, we’ve really dug into 3 solutions for that pesky error we all know too well: the ImportError: attempted relative import with no known parent package exception. Now, each solution has its perfect moment to shine.

While the first two might ask you for a bit of moving things around in the directory structure, the last one won’t. But, let’s tread carefully here. The last one’s a bit of a clever twist and it might be a bit fragile, potentially causing some name clashing. So, let’s agree to only pull it out of our magic hat when we really need to, shall we?