无法从 python 设置 pythonpath 环境变量

Question

I'm trying to debug a project that has a lot of additional libraries added to PYTHONPATH at runtime before launching the python file.

I was not able to add those commands with tasks.json file prior to debugging python file in Visual Studio code (see post Visual Studio Code unable to set env variable paths prior to debugging python file ), so I'm just adding them via an os.system("..") command

I'm only showing 1 of the libraries added below:

# Standard library imports
import os
import sys

os.system("SET PYTHONPATH=D:\\project\\calibration\\pylibrary\\camera")

# Pylibrary imports
from camera import capture

When I debug, it fails on line from camera import capture with:

Exception has occurred: ModuleNotFoundError
No module named 'camera'
  File "D:\project\main.py", line 12, in <module>
    from camera.capture import capture

I also tried

os.environ['PYTHONPATH']="D:\\project\\pylibrary\\camera" and I still get the same error

Why is it not remembering the pythonpath while running the script?

How else can I define the pythonpath while running Visual Studio Code and debugging the project file?

I know I can add the pythonpath to env variables in windows, but it loads too many libraries and I want it to only remember the path while the python script is executed.

Thanks

Answer 1

Using os.system() won't work because it starts a new cmd.exe shell and sets the env var in that shell. That won't affect the env vars of the python process. Assigning to os.environ['PYTHONPATH'] won't work because at that point your python process has already cached the value, if any, of that env var in the sys.path variable. The solution is to

import sys
sys.path.append(r"D:\project\calibration\pylibrary\camera")