Python – add PYTHONPATH during command line module run

I want to run:

python somescript.py somecommand

But, when I run this I need PYTHONPATH to include a certain directory. I can’t just add it to my environment variables because the directory I want to add changes based on what project I’m running. Is there a way to alter PYTHONPATH while running a script? Note: I don’t even have a PYTHONPATH variable, so I don’t need to worry about appending to it vs overriding it during running of this script.

Answers:

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Method 1

For Mac/Linux;

PYTHONPATH=/foo/bar/baz python somescript.py somecommand

For Windows, setup a wrapper pythonpath.bat;

@ECHO OFF
setlocal
set PYTHONPATH=%1
python %2 %3
endlocal

and call pythonpath.bat script file like;

pythonpath.bat /foo/bar/baz somescript.py somecommand

Method 2

 import sys
 sys.path.append('your certain directory')

Basically sys.path is a list with all the search paths for python modules. It is initialized by the interpreter. The content of PYTHONPATH is automatically added to the end of that list.

Method 3

If you are running the command from a POSIX-compliant shell, like bash, you can set the environment variable like this:

PYTHONPATH="/path/to" python somescript.py somecommand

If it’s all on one line, the PYTHONPATH environment value applies only to that one command.

$ echo $PYTHONPATH

$ python -c 'import sys;print("/tmp/pydir" in sys.path)'
False
$ PYTHONPATH=/tmp/pydir python -c 'import sys;print("/tmp/pydir" in sys.path)'
True
$ echo $PYTHONPATH

Method 4

You may try this to execute a function inside your script

python -c "import sys; sys.path.append('/your/script/path'); import yourscript; yourscript.yourfunction()"

Method 5

You can paste the following code in the __init__.py of the package from which you want to import:

import sys
from pathlib import Path


sys.path.insert(0, Path(__file__).parent)

Then you can import modules from that package as you would usually do.

import <module_name>

<module_name>.<method_on_module>()

Example:
import algorithms

algorithms.run_algo1()

Your IDE might underline the module name, but that won’t be a problem when you run the Python interpreted.

Also, if you need to read the path, later on, you can do:

DIR_PATH = Path(sys.path[0])

Method 6

This is for windows:

For example, I have a folder named “mygrapher” on my desktop. Inside, there’s folders called “calculation” and “graphing” that contain Python files that my main file “grapherMain.py” needs. Also, “grapherMain.py” is stored in “graphing”. To run everything without moving files, I can make a batch script. Let’s call this batch file “rungraph.bat”.

@ECHO OFF
setlocal
set PYTHONPATH=%cd%grapher;%cd%calculation
python %cd%graphergrapherMain.py
endlocal

This script is located in “mygrapher”. To run things, I would get into my command prompt, then do:

>cd Desktopmygrapher (this navigates into the "mygrapher" folder)
>rungraph.bat (this executes the batch file)

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0