How to do relative imports in Python?

The Question :

539 people think this question is useful

Imagine this directory structure:

app/
__init__.py
sub1/
__init__.py
mod1.py
sub2/
__init__.py
mod2.py



I’m coding mod1, and I need to import something from mod2. How should I do it?

I tried from ..sub2 import mod2 but I’m getting an “Attempted relative import in non-package”.

I googled around but found only “sys.path manipulation” hacks. Isn’t there a clean way?

Edit: all my __init__.py‘s are currently empty

Edit2: I’m trying to do this because sub2 contains classes that are shared across sub packages (sub1, subX, etc.).

Edit3: The behaviour I’m looking for is the same as described in PEP 366 (thanks John B)

The Question Comments :
• I recommend updating your question to make it more clear that you’re describing the issue addressed in PEP 366.
• It’s a long winded explanation but check here: stackoverflow.com/a/10713254/1267156 I answered a very similar question. I had this same problem until last night.
• For those who wish to load a module located at an arbitrary path, see this: stackoverflow.com/questions/67631/…
• On a related note, Python 3 will change the default handling of imports to be absolute by default; relative imports will have to be explicitly specified.

The Answer 1

345 people think this answer is useful

Everyone seems to want to tell you what you should be doing rather than just answering the question.

The problem is that you’re running the module as ‘__main__’ by passing the mod1.py as an argument to the interpreter.

From PEP 328:

Relative imports use a module’s __name__ attribute to determine that module’s position in the package hierarchy. 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.

In Python 2.6, they’re adding the ability to reference modules relative to the main module. PEP 366 describes the change.

Update: According to Nick Coghlan, the recommended alternative is to run the module inside the package using the -m switch.

The Answer 2

136 people think this answer is useful

Here is the solution which works for me:

I do the relative imports as from ..sub2 import mod2 and then, if I want to run mod1.py then I go to the parent directory of app and run the module using the python -m switch as python -m app.sub1.mod1.

The real reason why this problem occurs with relative imports, is that relative imports works by taking the __name__ property of the module. If the module is being directly run, then __name__ is set to __main__ and it doesn’t contain any information about package structure. And, thats why python complains about the relative import in non-package error.

So, by using the -m switch you provide the package structure information to python, through which it can resolve the relative imports successfully.

I have encountered this problem many times while doing relative imports. And, after reading all the previous answers, I was still not able to figure out how to solve it, in a clean way, without needing to put boilerplate code in all files. (Though some of the comments were really helpful, thanks to @ncoghlan and @XiongChiamiov)

Hope this helps someone who is fighting with relative imports problem, because going through PEP is really not fun.

The Answer 3

125 people think this answer is useful
main.py
setup.py
app/ ->
__init__.py
package_a/ ->
__init__.py
module_a.py
package_b/ ->
__init__.py
module_b.py


1. You run python main.py.
2. main.py does: import app.package_a.module_a
3. module_a.py does import app.package_b.module_b

Alternatively 2 or 3 could use: from app.package_a import module_a

That will work as long as you have app in your PYTHONPATH. main.py could be anywhere then.

So you write a setup.py to copy (install) the whole app package and subpackages to the target system’s python folders, and main.py to target system’s script folders.

The Answer 4

50 people think this answer is useful

“Guido views running scripts within a package as an anti-pattern” (rejected PEP-3122)

I have spent so much time trying to find a solution, reading related posts here on Stack Overflow and saying to myself “there must be a better way!”. Looks like there is not.

The Answer 5

38 people think this answer is useful

This is solved 100%:

• app/
• main.py
• settings/
• local_setings.py

Import settings/local_setting.py in app/main.py:

main.py:

import sys
sys.path.insert(0, "../settings")

try:
from local_settings import *
except ImportError:
print('No Import')



The Answer 6

24 people think this answer is useful
def import_path(fullpath):
"""
Import a file with full path specification. Allows one to
import from anywhere, something __import__ does not do.
"""
path, filename = os.path.split(fullpath)
filename, ext = os.path.splitext(filename)
sys.path.append(path)
module = __import__(filename)
reload(module) # Might be out of date
del sys.path[-1]
return module



I’m using this snippet to import modules from paths, hope that helps

The Answer 7

22 people think this answer is useful

explanation of nosklo's answer with examples

note: all __init__.py files are empty.

main.py
app/ ->
__init__.py
package_a/ ->
__init__.py
fun_a.py
package_b/ ->
__init__.py
fun_b.py



app/package_a/fun_a.py

def print_a():
print 'This is a function in dir package_a'



app/package_b/fun_b.py

from app.package_a.fun_a import print_a
def print_b():
print 'This is a function in dir package_b'
print 'going to call a function in dir package_a'
print '-'*30
print_a()



main.py

from app.package_b import fun_b
fun_b.print_b()



if you run $python main.py it returns: This is a function in dir package_b going to call a function in dir package_a ------------------------------ This is a function in dir package_a  • main.py does: from app.package_b import fun_b • fun_b.py does from app.package_a.fun_a import print_a so file in folder package_b used file in folder package_a, which is what you want. Right?? The Answer 8 12 people think this answer is useful This is unfortunately a sys.path hack, but it works quite well. I encountered this problem with another layer: I already had a module of the specified name, but it was the wrong module. what I wanted to do was the following (the module I was working from was module3): mymodule\ __init__.py mymodule1\ __init__.py mymodule1_1 mymodule2\ __init__.py mymodule2_1 import mymodule.mymodule1.mymodule1_1  Note that I have already installed mymodule, but in my installation I do not have “mymodule1” and I would get an ImportError because it was trying to import from my installed modules. I tried to do a sys.path.append, and that didn’t work. What did work was a sys.path.insert if __name__ == '__main__': sys.path.insert(0, '../..')  So kind of a hack, but got it all to work! So keep in mind, if you want your decision to override other paths then you need to use sys.path.insert(0, pathname) to get it to work! This was a very frustrating sticking point for me, allot of people say to use the “append” function to sys.path, but that doesn’t work if you already have a module defined (I find it very strange behavior) The Answer 9 10 people think this answer is useful Let me just put this here for my own reference. I know that it is not good Python code, but I needed a script for a project I was working on and I wanted to put the script in a scripts directory. import os.path import sys sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))  The Answer 10 9 people think this answer is useful As @EvgeniSergeev says in the comments to the OP, you can import code from a .py file at an arbitrary location with: import imp foo = imp.load_source('module.name', '/path/to/file.py') foo.MyClass()  This is taken from this SO answer. The Answer 11 5 people think this answer is useful Take a look at http://docs.python.org/whatsnew/2.5.html#pep-328-absolute-and-relative-imports. You could do from .mod1 import stuff  The Answer 12 2 people think this answer is useful From Python doc, In Python 2.5, you can switch import‘s behaviour to absolute imports using a from __future__ import absolute_import directive. This absolute- import behaviour will become the default in a future version (probably Python 2.7). Once absolute imports are the default, import string will always find the standard library’s version. It’s suggested that users should begin using absolute imports as much as possible, so it’s preferable to begin writing from pkg import string in your code The Answer 13 1 people think this answer is useful I found it’s more easy to set “PYTHONPATH” enviroment variable to the top folder: bash$ export PYTHONPATH=/PATH/TO/APP



then:

import sub1.func1
#...more import



of course, PYTHONPATH is “global”, but it didn’t raise trouble for me yet.

The Answer 14

1 people think this answer is useful

On top of what John B said, it seems like setting the __package__ variable should help, instead of changing __main__ which could screw up other things. But as far as I could test, it doesn’t completely work as it should.

I have the same problem and neither PEP 328 or 366 solve the problem completely, as both, by the end of the day, need the head of the package to be included in sys.path, as far as I could understand.

I should also mention that I did not find how to format the string that should go into those variables. Is it "package_head.subfolder.module_name" or what?

The Answer 15

0 people think this answer is useful

You have to append the module’s path to PYTHONPATH:

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