Is there a better way to set sys.path.append in python project?

Question

I have a simple python project with the following directory structure:

sample-project/
main/
    config/
        config.yaml
    docker/
        Dockerfile
    tests/
        __init__.py
        sometests.py
    config.py
    run.py
    __init__.py
requirements.txt
README.rst

In the config.py file, I have:

import yaml


class Config:

def __init__(self):
    with open("config/config.yaml", 'r') as ymlfile:
        cfg = yaml.load(ymlfile)

        self.host = cfg["mysql"]["host"]
        self.database = cfg["mysql"]["database"]
        self.user = cfg["mysql"]["user"]
        self.password = cfg["mysql"]["password"]


my_config = Config()

In the run.py file, I have an import statement as follows:

from main.config import my_config

when I run using command line: python3.5 run.py, I get the error:

from main.config import my_config

ImportError: No module named 'main'

But when I add this in run.py imports it works:

import sys
sys.path.append('/home/tomas/sample-project/')

Is there any better way to make it work rather than give absolute path or any other way? Please give some example :)

Answer 1

Generally, never ever touch sys.path from within your program.

Since main/ (not the best name) contains an __init__.py, we'll consider it a package, so let's make it runnable as one. This way imports will be considered correctly.

Add main/__main__.py with e.g.

from main.run import run

if __name__ == "__main__":
   run()

Then run your app with

python -m main

instead of

python main/main.py

Answer 2

when mentioning below from main.config import my_config

keep dir path also eg: from sample-project/main.config import my_config

assuming you are executing from /home/tomas

Answer 3

Although I share AKX's sentiment that editing your path is something to avoid I would generally suggest the following method:

import sys
from os.path import dirname
abs_dir = dirname(__file__)
sys.path.append(abs_dir)

The __file__ variable provides access to the location of the file in which it is accessed. This allows you to get an absolute path to any file in your project.