ImportError: libopenblas.so.0: cannot open shared object file: No such file or directory

TL;DR: numpy needs the OpenBLAS shared library and your system does not provide it. Install the OpenBLAS runtime package for your Linux distro, or reinstall numpy from a wheel that bundles OpenBLAS. Then import numpy works.

The error

ImportError: libopenblas.so.0: cannot open shared object file: No such file or directory

Fix it

1. Install the OpenBLAS runtime package. On Debian/Ubuntu:

   sudo apt install libopenblas0

   On RHEL/Fedora: sudo dnf install openblas. Expected: the package installs without errors.

2. Verify the library is now visible:

   ldconfig -p | grep libopenblas

   Expected: a line showing libopenblas.so.0.

3. Retry the import:

   python -c "import numpy; print(numpy.__version__)"

   Expected: prints the version, no error.

4. Alternative if you cannot install system packages: force a numpy wheel that bundles its own OpenBLAS:

   pip install --force-reinstall numpy

   Expected: the fresh wheel imports cleanly.

When this applies

Use this when import numpy (or scipy, which shares the dependency) fails on Linux with the libopenblas.so.0 message.

When it does not apply

On Windows or macOS numpy wheels bundle their own BLAS, so this error there means something else. If the missing file is a different .so, install that library instead.

Compatibility

Linux, numpy/scipy built against system OpenBLAS (common with distro-packaged python or some cluster setups). Official PyPI manylinux wheels bundle OpenBLAS and do not hit this.

Root cause

numpy links against the OpenBLAS linear-algebra library at import time. Some installs link the system copy instead of a bundled one, so a machine without the OpenBLAS runtime package fails the dynamic load.

Edge cases

On HPC clusters the fix is usually module load of the right environment module rather than apt. In minimal docker images, add the package to the Dockerfile. If ldconfig still cannot see it after install, run sudo ldconfig once.