How do you add a path to PYTHONPATH in a Dockerfile

Question

How do you add a path to PYTHONPATH in a Dockerfile? So that when the container is run it has the correct PYTHONPATH? I'm completely new to Docker.

I've added ENV PYTHONPATH "${PYTHONPATH}:/control" to the Dockerfile as I want to add the directory /control to PYTHONPATH.

When I access the container's bash with docker exec -it trusting_spence bash and open python and run the commands below the directory control is not on the list.

import sys print(sys.path)

FROM python:2
RUN pip install requests pymongo

RUN mkdir control

COPY control_file/ /control

ENV PYTHONPATH "${PYTHONPATH}:/control"

CMD ["python","control/control_file/job.py"]

CyberPlayerOne · Accepted Answer · 2024-07-14 04:04:26Z

159

Just add an ENV entry in your Dockerfile:

ENV PYTHONPATH="${PYTHONPATH}:/your/custom/path"

Or set PYTHONPATH in your startup script.

edited Jul 14, 2024 at 4:04

CyberPlayerOne

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answered Apr 3, 2018 at 13:31

Erik Cederstrand

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9 Comments

arcoxia tom Over a year ago

I tried your suggestion without success, I've edited my original post to include my steps. Could you suggest what I'm doing wrong?

Miek Over a year ago

Did you try it with the typo fixed in the string? "${PYTHONPATH}:/your/custom/path"

physincubus Over a year ago

for one reason or another, this is still just overwriting my PYTHONPATH. Additionally, while this is modifying the ENV variable, my path according to python -c "import sys; for p in sys.path: print(p)" is still unchanged, containing only the old (seemingly overwritten) PYTHONPATH, which none of the changes

Amir Over a year ago

The answer is correct, it's probably not working for some people because your're using the wrong path. if your module is named "mymodule" and it located at /src/mymodule then you should have: ENV PYTHONPATH "${PYTHONPATH}:/src"

Erik Cederstrand Over a year ago

The OP afsked about adding to PYTHONPATH. If you don’t have that var defined already, then just do ENV PYTHONPATH=/foo

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Nimrod Morag · Accepted Answer · 2019-01-20 10:49:04Z

You're setting the python path correctly, but your command is not being run by a shell, so the environment variable PYTHONPATH is not considered.

chang your CMD from "exec" form to "shell" form:

CMD python control/control_file/job.py

From the Docs:

Note: Unlike the shell form, the exec form does not invoke a command shell. This means that normal shell processing does not happen. For example, CMD [ "echo", "$HOME" ] will not do variable substitution on $HOME. If you want shell processing then either use the shell form or execute a shell directly, for example: CMD [ "sh", "-c", "echo $HOME" ]. When using the exec form and executing a shell directly, as in the case for the shell form, it is the shell that is doing the environment variable expansion, not docker.

unlockme · Accepted Answer · 2019-10-09 12:46:44Z

5

Do it in a much simpler way. Add the python path in your .env file as a line in this way.

PYTHONPATH=/app/project_source/

answered Oct 9, 2019 at 12:46

unlockme

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