Importing Python modules from different working directory

Question

I have a Python script that uses built-in modules but also imports a number of custom modules that exist in the same directory as the main script itself.

For example, I would call

python agent.py

and agent.py has a number of imports, including:

import checks

where checks is in a file in the same directory as agent.py

agent/agent.py
agent/checks.py

When the current working directory is agent/ then everything is fine. However, if I call agent.py from any other directory, it is obviously unable to import checks.py and so errors.

How can I ensure that the custom modules can be imported regardless of where the agent.py is called from e.g.

python /home/bob/scripts/agent/agent.py

Answer 1

Actually your example works because checks.py is in the same directory as agent.py, but say checks.py was in the preceeding directory, eg;

agent/agent.py
checks.py

Then you could do the following:

path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not path in sys.path:
    sys.path.insert(1, path)
del path

Note the use of __file__.

Answer 2

You should NOT need to fiddle with sys.path. To quote from the Python 2.6 docs for sys.path:

As initialized upon program startup, the first item of this list, path[0], is the directory containing the script that was used to invoke the Python interpreter. If the script directory is not available (e.g. if the interpreter is invoked interactively or if the script is read from standard input), path[0] is the empty string, which directs Python to search modules in the current directory first. Notice that the script directory is inserted before the entries inserted as a result of PYTHONPATH.

=== amod.py ===
def whoami():
    return __file__

=== ascript.py ===
import sys
print "sys.argv", sys.argv
print "sys.path", sys.path
import amod
print "amod __file__", amod.whoami()

=== result of running ascript.py from afar ===
C:\somewhere_else>\python26\python \junk\timport\ascript.py
sys.argv ['\\junk\\timport\\ascript.py']
sys.path ['C:\\junk\\timport', 'C:\\WINDOWS\\system32\\python26.zip', SNIP]
amod __file__ C:\junk\timport\amod.py

and if it's re-run, the last line changes of course to ...amod.pyc. This appears not to be a novelty, it works with Python 2.1 and 1.5.2.

Debug hints for you: Try two simple files like I have. Try running Python with -v and -vv. Show us the results of your failing tests, including full traceback and error message, and your two files. Tell us what platform you are running on, and what version of Python. Check the permissions on the checks.py file. Is there a checks.something_else that's causing interference?

Answer 3

You need to add the path to the currently executing module to the sys.path variable. Since you called it on the command line, the path to the script will always be in sys.argv[0].

import sys
import os
sys.path.append(os.path.split(sys.argv[0])[0])

Now when import searches for the module, it will also look in the folder that hosts the agent.py file.

Answer 4

There are several ways to add things to the PYTHONPATH.

Read http://docs.python.org/library/site.html

1. Set the PYTHONPATH environment variable prior to running your script.

   You can do this python -m agent to run agent.py from your PYTHONPATH.

2. Create .pth files in your lib/site-packages directory.

3. Install your modules in lib/site-packages.

Answer 5

I think you should consider making the agent directory into a proper Python package. Then you place this package anywhere on the python path, and you can import checks as

from agent import checks

See http://docs.python.org/tutorial/modules.html

Answer 6

If you know full path to check.py use this recipe (http://code.activestate.com/recipes/159571/)

If you want to add directory to system path -- this recipe (http://code.activestate.com/recipes/52662/). In this case I have to determine application directory (sys.argv[0]) an pass this value to AddSysPath function. If you want to look at production sample please leave a comment on this thread so I post it later.

Regards.

Answer 7

To generalize my understanding of your goal, you want to be able to import custom packages using import custom_package_name no matter where you are calling python from and no matter where your python script is located.

A number of answers mention what I'm about to describe, but I feel like most of the answers assume a lot of previous knowledge. I'll try to be as explicit as I can.

To achieve the goal of allowing custom packages to be imported via the import statement, they have to be discoverable somewhere through the path that python uses to search for packages. Python actually uses multiple paths, but we'll only focus on the one that can be found by combining the output of sys.prefix (in your python interpreter) with /lib/pythonX.Y/site-packages (or lib/site-packages if you're using windows) where X.Y is your python version.

Concretely, find the path that your python uses by running:

import sys
your_path = sys.prefix + '/lib/pythonX.Y/site-packages'
print(your_path)

This path should look something like /usr/local/lib/python3.5/site-packages if you're using python 3.5, but it could be much different depending on your setup.

Python uses this path (and a few others) to find the packages that you want to import. So what you can do is put your custom packages in the /usr/local/lib/python3.5/site-packages folder. Don't forget to add an init.py file to the folder.

To be concrete again, in terminal type:

cd your_path
cp path_to_custom_package/custom_package ./

Now you should be able to import everything your custom package like you would if the package was located in the same directory (i.e. import package.subpackage for each subpackage file in your package should work).