Question: It says numpy not installed even though it is installed. I thought may be the venv is not accessible to pip (which it should be, because numpy is installed inside the venv) and I installed it system wide using sudo apt install python3-numpy as you can see in the very last of the following snippet. vanangamudi@kaithadi:~/code/bec-gp/BEC_GP $ workon gpinn (gpinn) vanangamudi@kaithadi:~/code/bec-gp/BEC_GP $ pip install trottersuzuki Collecting trottersuzuki Using cached trottersuzuki-1.6.2.tar.gz (218 kB) Installing build dependencies ... done Getting requirements to build wheel ... error error: subprocess-exited-with-error × Getting requirements to build wheel did not run successfully. │ exit code: 1 ╰─> [20 lines of output] Traceback (most recent call last): File "/home/vanangamudi/.virtualenvs/gpinn/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module> main() File "/home/vanangamudi/.virtualenvs/gpinn/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main json_out['return_val'] = hook(**hook_input['kwargs']) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/home/vanangamudi/.virtualenvs/gpinn/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel return hook(config_settings) ^^^^^^^^^^^^^^^^^^^^^ File "/tmp/pip-build-env-d6cdwe1m/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 332, in get_requires_for_build_wheel return self._get_build_requires(config_settings, requirements=[]) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/tmp/pip-build-env-d6cdwe1m/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 302, in _get_build_requires self.run_setup() File "/tmp/pip-build-env-d6cdwe1m/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 503, in run_setup super().run_setup(setup_script=setup_script) File "/tmp/pip-build-env-d6cdwe1m/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 318, in run_setup exec(code, locals()) File "<string>", line 6, in <module> ModuleNotFoundError: No module named 'numpy' [end of output] note: This error originates from a subprocess, and is likely not a problem with pip. error: subprocess-exited-with-error × Getting requirements to build wheel did not run successfully. │ exit code: 1 ╰─> See above for output. note: This error originates from a subprocess, and is likely not a problem with pip. (gpinn) vanangamudi@kaithadi:~/code/bec-gp/BEC_GP $ python -c 'import numpy' (gpinn) vanangamudi@kaithadi:~/code/bec-gp/BEC_GP $ python -c 'import matplotlib' Traceback (most recent call last): File "<string>", line 1, in <module> ModuleNotFoundError: No module named 'matplotlib' (gpinn) vanangamudi@kaithadi:~/code/bec-gp/BEC_GP $ 

Answer: trottersuzuki doesn't provide binary wheels, only sdist. When installing from a source distribution modern pip first build a wheel in a new isolated virtual environment. In this isolated venv there is no numpy. For pip to install numpy during build phase there must be a file pyproject.toml in the package that lists numpy as a build dependency. But there is no such file. I advice to report it… oh, I see you've already reported the bug; you should told this in the question. Until the bug is fixed there is workaround: disable build isolation: $ pip install numpy setuptools $ pip install --no-build-isolation trottersuzuki