How to do relative imports in Python?

Joril_3497 0
Viewed 381328

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)

python-module python-import python
17 Answers

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.

John_B_95970 
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.

user_171600 
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

user_1332350

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.

user_4517180

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

export PYTHONPATH="${PYTHONPATH}:/path/to/your/module/"
user_71317570

This method queries and auto populates the path:

import os
import inspect
currentdir = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
parentdir = os.path.dirname(currentdir)
os.sys.path.insert(1, parentdir)
# print("currentdir = ", currentdir)
# print("parentdir=", parentdir)
user_143761810

A hacky way to do it is to append the current directory to the PATH at runtime as follows:

import pathlib   
import sys
sys.path.append(pathlib.Path(__file__).parent.resolve())
import file_to_import  # the actual intended import

In contrast to another solution for this question this uses pathlib instead of os.path.

user_48588180
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