Struggling to get a Python shell with pandas/numpy available

[fvicent]

Hi there. I've been using nixpacks in Railway for a while, but I'm also pretty new to the nix universe in general. Basically, I have a Python application which depends on pandas, which depends on numpy. Here's an equivalent nixpacks.toml which reproduces the error:

[variables]
NIXPACKS_PYTHON_VERSION = "3.10"

[phases.setup]
nixPkgs = ["...", "python310Packages.pandas", "python310Packages.numpy"]

[phases.install]
cmds = [
    "python -m venv /opt/venv",
    ". /opt/venv/bin/activate",
    "pip install -r requirements.txt",
]

[start]
cmd = "python -c \"import pandas; print(pandas)\""

And the requirements.txt file:

pandas==2.2.3

Now I can build and run this image without problems. Pandas is in fact available from the virtualenv:

nixpacks build . --name pandastest
docker run -it pandastest                  
<module 'pandas' from '/opt/venv/lib/python3.10/site-packages/pandas/__init__.py'>

The problem is when trying to import pandas from a Python shell:

docker run -it --entrypoint bash pandastest
root@fb4d21ee17c4:/app# . /opt/venv/bin/activate
(venv) root@fb4d21ee17c4:/app# python
Python 3.10.15 (main, Sep  7 2024, 00:20:06) [GCC 13.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/venv/lib/python3.10/site-packages/pandas/__init__.py", line 19, in <module>
    raise ImportError(
ImportError: Unable to import required dependencies:
numpy: Error importing numpy: you should not try to import numpy from
        its source directory; please exit the numpy source tree, and relaunch
        your python interpreter from there.

If I then try to import numpy, I can see the underlying error:

>>> import numpy
Traceback (most recent call last):
  File "/opt/venv/lib/python3.10/site-packages/numpy/_core/__init__.py", line 23, in <module>
    from . import multiarray
  File "/opt/venv/lib/python3.10/site-packages/numpy/_core/multiarray.py", line 10, in <module>
    from . import overrides
  File "/opt/venv/lib/python3.10/site-packages/numpy/_core/overrides.py", line 7, in <module>
    from numpy._core._multiarray_umath import (
ImportError: libstdc++.so.6: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/venv/lib/python3.10/site-packages/numpy/__init__.py", line 114, in <module>
    from numpy.__config__ import show_config
  File "/opt/venv/lib/python3.10/site-packages/numpy/__config__.py", line 4, in <module>
    from numpy._core._multiarray_umath import (
  File "/opt/venv/lib/python3.10/site-packages/numpy/_core/__init__.py", line 49, in <module>
    raise ImportError(msg)
ImportError:

IMPORTANT: PLEASE READ THIS FOR ADVICE ON HOW TO SOLVE THIS ISSUE!

Importing the numpy C-extensions failed. This error can happen for
many reasons, often due to issues with your setup or how NumPy was
installed.

We have compiled some common reasons and troubleshooting tips at:

    https://numpy.org/devdocs/user/troubleshooting-importerror.html

Please note and check the following:

  * The Python version is: Python3.10 from "/opt/venv/bin/python"
  * The NumPy version is: "2.2.6"

and make sure that they are the versions you expect.
Please carefully study the documentation linked above for further help.

Original error was: libstdc++.so.6: cannot open shared object file: No such file or directory


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/venv/lib/python3.10/site-packages/numpy/__init__.py", line 119, in <module>
    raise ImportError(msg) from e
ImportError: Error importing numpy: you should not try to import numpy from
        its source directory; please exit the numpy source tree, and relaunch
        your python interpreter from there.

This seems to be very nix-specific. So I found this discussion in the NixOS forum which addresses the same NumPy error and suggests a solution to get a pandas-powered Python shell. However, I'm not sure how to do the same thing with nixpacks. Could someone please point me in the right direction?

Regards,
Francisco