sys.path list

sys.path list#

You can add any elements to the sys.path. Following cells are examples of this feature.

Let’s save a module that just prints something, so that every time it is imported, this message appears in the terminal.

%%writefile imports_files/test_module.py
print("this file was imported")

Writing imports_files/test_module.py

Module from the previous cell is saved in a package that is not in sys.path. Therefore, when trying to import it, an error is raised, as shown in the next cell:

try:
    import test_module
except ModuleNotFoundError:
    print("ModuleNotFoundError was rised")

ModuleNotFoundError was rised

But if you’ve added a folder that contains the module in question, it will be imported just fine:

sys.path.append("imports_files")
import test_module
sys.path.remove("imports_files")

Environment variable#

You can define the environment variable PYTHONPATH and list the paths with “:” - they will automatically appear in the sys.path of python running in that environment.

In the following cell we have run some code that defines PYTHONPATH as two paths separated by “:”, then run a script that prints out sys.path. As a result you can see that the mentioned paths have been added to the sys.path list.

%%bash
export PYTHONPATH="example/path1:example/path2"
echo $PYTHONPATH

echo
echo "=====python output====="
python3 path_settings_files/print_sys_folder.py

example/path1:example/path2

=====python output=====
/home/f.kobak@maxbit.local/Documents/knowledge/python/basics/path_settings_files
/home/f.kobak@maxbit.local/Documents/knowledge/python/basics/example/path1
/home/f.kobak@maxbit.local/Documents/knowledge/python/basics/example/path2
/usr/lib/python310.zip
/usr/lib/python3.10
/usr/lib/python3.10/lib-dynload
/home/f.kobak@maxbit.local/.local/lib/python3.10/site-packages
/usr/local/lib/python3.10/dist-packages
/usr/lib/python3/dist-packages
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