Most likely due to a circular import python как исправить

Consider the following example python package where a.py and b.py depend on each other:

/package
    __init__.py
    a.py
    b.py

Types of circular import problems

Circular import dependencies typically fall into two categories depending
on what you’re trying to import and where you’re using it inside each
module. (And whether you’re using python 2 or 3).

1. Errors importing modules with circular imports

In some cases, just importing a module with a circular import dependency
can result in errors even if you’re not referencing anything from the
imported module.

There are several standard ways to import a module in python

import package.a           # (1) Absolute import
import package.a as a_mod  # (2) Absolute import bound to different name
from package import a      # (3) Alternate absolute import
import a                   # (4) Implicit relative import (deprecated, python 2 only)
from . import a            # (5) Explicit relative import

Unfortunately, only the 1st and 4th options actually work when you
have circular dependencies (the rest all raise ImportError
or AttributeError). In general, you shouldn’t be using the
4th syntax, since it only works in python2 and runs the risk of
clashing with other 3rd party modules. So really, only the first
syntax is guaranteed to work.

EDIT: The ImportError and AttributeError issues only occur in
python 2. In python 3 the import machinery has been rewritten and all
of these import statements (with the exception of 4) will work, even with
circular dependencies. While the solutions in this section may help refactoring python 3 code, they are mainly intended
for people using python 2.

Absolute Import

Just use the first import syntax above. The downside to this method is
that the import names can get super long for large packages.

In a.py

import package.b

In b.py

import package.a

Defer import until later

I’ve seen this method used in lots of packages, but it still feels
hacky to me, and I dislike that I can’t look at the top of a module
and see all its dependencies, I have to go searching through all the
functions as well.

In a.py

def func():
    from package import b

In b.py

def func():
    from package import a

Put all imports in a central module

This also works, but has the same problem as the first method, where
all the package and submodule calls get super long. It also has two
major flaws — it forces all the submodules to be imported, even if
you’re only using one or two, and you still can’t look at any of the
submodules and quickly see their dependencies at the top, you have to
go sifting through functions.

In __init__.py

from . import a
from . import b

In a.py

import package

def func():
    package.b.some_object()

In b.py

import package

def func():
    package.a.some_object()

2. Errors using imported objects with circular dependencies

Now, while you may be able to import a module with a circular import
dependency, you won’t be able to import any objects defined in the module
or actually be able to reference that imported module anywhere
in the top level of the module where you’re importing it. You can,
however, use the imported module inside functions and code blocks that don’t
get run on import.

For example, this will work:

package/a.py

import package.b

def func_a():
    return "a"

package/b.py

import package.a

def func_b():
    # Notice how package.a is only referenced *inside* a function
    # and not the top level of the module.
    return package.a.func_a() + "b"

But this won’t work

package/a.py

import package.b

class A(object):
    pass

package/b.py

import package.a

# package.a is referenced at the top level of the module
class B(package.a.A):
    pass

You’ll get an exception

AttributeError: module ‘package’ has no attribute ‘a’

Generally, in most valid cases of circular dependencies, it’s possible
to refactor or reorganize the code to prevent these errors and move
module references inside a code block.

We love to use modules in Python and why not, they provide additional functionalities, better coding practice, and always create a proper structure while using. But many times unknowingly, we can run into python circular import problems if we accidentally have another file named as module’s name. As python prefers importing from the local current directory first and then from site-packages, it will create a circular import problem.

Generally, the Python Circular Import problem occurs when you accidentally name your working file the same as the module name and those modules depend on each other. This way the python opens the same file which causes a circular loop and eventually throws an error.

For example, when you name your file as random.py and try to import “from random import randint”, it’ll throw a circular import error (also termed as from partially initialized module).

In this post, we’ll have a look at all the causes and their solutions for circular import.

How Circular Import Is Identified?

Then a module calls an object within itself, circular import error is raised. Let’s consider an example where you are working on a ‘rea.py’ python file and you write a code as ‘from rea import x’. This will cause python to import the object x from the rea module.

This will cause a circular call within the code and it’ll throw an exception with an error mentioned as “ImportError: cannot import name ‘x’ from partially initialized module ‘rea’ (most likely due to a circular import) (/home/pythonpool/rea.py)”.

This exception is raised when you try to import any type of object. There are no exceptions.

Tip: Circular import is only raised when you import object from module. It is not raised when you try to import module itself. So, in above example, “import rea” will work just fine.

How to fix Python Circular Import?

There are several workarounds to solve the circular import problem. Each of these workarounds has its different use cases. Make sure you use the solution that suits best for your problem.

Conditional Import is also one of the ways by which you can handle such cases but does not try to use try-except blocks to fix circular imports as the core problem of importing variables still remain even if we ignore it.

Importing The Module Itself

There is a good workaround Python circular import error that you can import the module itself rather than importing object/function from the module. This way you can import and use all the objects and variables from the module.

Suppose, a module named module_name has function func_name, and you want to import it but it throws a circular error.

The easiest way to make this work is by importing the module_name itself. The following example will help you to understand it –

rea.py –

import rea

x=1

if __name__ == '__main__':
    print(rea.x)

Even if you are calling the same module, it’ll work. Use these cases to fix the issues in flask and Django where the filenames can match the pre-defined module names.

Rename Your Working file

Sometimes, we can name our working file to module name without knowing its consequences (Even I did it many times :P). Renaming the file will work perfectly in such cases. For example, if you want to use the numpy module, you should avoid your working file naming numpy.py.

Here’s an example –

– numpy.py –

from numpy import array

x = array([1, 2, 3])

ImportError: cannot import name 'array' from partially initialized module 'numpy' (most likely due to a circular import) (/home/pythonpool/numpy.py)

Now, rename our working file to a different name –

– pool_numpy.py –

from numpy import array

x = array([1, 2, 3])
print(x)

[1 2 3]

Just as we avoid naming variables to built-in variables to avoid issues, you need to avoid naming your file to module name to avoid conflicts.

Avoid Circular Import Calls

Consider the following example –

– module1.py –

from module2 import func2

def func1():
	func2()

– module2.py –

from module1 import func1

def func2():
	func1()

Command to run –

python .module1.py
Traceback (most recent call last):
  File "/home/pythonpool/module1.py", line 1, in <module>
    from module2 import func2
  File "/home/pythonpool/module2.py", line 1, in <module>
    from module1 import func1
  File "/home/pythonpool/module1.py", line 1, in <module>
    from module2 import func2
ImportError: cannot import name 'func2' from partially initialized module 'module2' (most likely due to a circular import) (/home/pythonpool/module2.py)

The above example demonstrates a situation where you try to import a variable from module2 which is partially initialized (python doesn’t know that func2 even exists or not).

In such cases try to copy the required function/object to your working file.

In the above example, if you declare func2 itself in module1, it’ll not be of any problem.

Solve Circular Import Error In Django

Ever tried importing Django modules/classes in your Django project? You’ll definitely encounter a python circular import error once in such scenarios. If you try to implement the Django model manually by directly importing it, it’ll throw an error.

For example, you have your Django installed apps as follows –

INSTALLED_APPS = (
    'app1',
)

And you want to use the structure of app1, you might import it directly in your python file considering its installed app. Something like this –

from app1.models import App1

Then most likely, you’ll encounter the python circular import error in your code. This is the incorrect way of importing a Model in your Django Application. Following is the correct way to do it –

For Django <=1.7:

from django.db.models import get_model
MyModel = get_model('app1',  'App1')

For Django > 1.7:

from django.apps import apps
apps.get_model('app1.App1')

This way the model ‘App1’ from app ‘app1’ will be imported into your Django application directly.

Solution for Python Circular Import Error In Flask

Similar to Django, flask also has circular import issues especially when you’re dealing with SQLAlchemy. If you try to use the database model of SQLAlchemy (declared in the main app file) in a different file, it’ll throw a circular import error.

Consider the following examples –

– app.py –

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__ name __)
db = SQLAlchemy(app)  
from models import routes

– routes.py –

This is indeed a circular import as app.py called routes and routes call DB from app.py. To fix such issues we create a separate extension for a database where we initialize the SQLAlchemy database.

from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()

This can be imported in app.py and models.py and used accordingly.

FAQs

References

Python Import System: How searching of Modules works in Python.

Новичок в python. Пытался разобраться в colorama и написал такой код:

from colorama import *
init()


print(Style.DIM)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)
print(Fore.GREEN)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)
print(Back.YELLOW)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)
"""
Fore: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
Back: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
Style: DIM, NORMAL, BRIGHT, RESET_ALL
"""

Запускаю… Ошибка
NameError: name ‘init’ is not defined
Убираю init()
Та же ошибка,
Заменяю код на

from colorama import init
init()


print(Style.DIM)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)
print(Fore.GREEN)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)
print(Back.YELLOW)
print("Это рыбный текст в к0тором я поместил все буквы алфавита. Читать его не имеет смысла так, как мне лень дальше писать")
print(Style.RESET_ALL)

Ошибка
ImportError: cannot import name ‘init’ from partially initialized module ‘colorama’ (most likely due
to a circular import)