ImportError: DLL load failed while importing lib

TL;DR: pyarrow's bundled native library will not load on your Windows box. Reinstall pyarrow from a fresh wheel and make sure the Visual C++ redistributable is installed.

The error

ImportError: DLL load failed while importing lib

Fix it

1. Reinstall pyarrow cleanly:

   pip install --force-reinstall pyarrow

Expected: downloads and installs a fresh wheel.

1. Make sure the Visual C++ redistributable (2015 or later) is installed on the machine; pyarrow's DLLs need it. Expected: installer completes.
2. Verify:

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

Expected: prints the version, no DLL error.

When this applies

Use this when import pyarrow on Windows raises the DLL load failed message.

When it does not apply

On Linux or macOS this specific message does not occur; look for the platform's own shared-library error. If a different DLL name is missing, install that component instead.

Compatibility

Windows, pyarrow wheels with bundled native libs.

Root cause

pyarrow ships compiled C++ libraries inside the wheel. If the wheel download was corrupt, partially overwritten, or the system C++ runtime is missing, Windows cannot load the bundled lib and Python surfaces this terse error.

Edge cases

Antivirus quarantining the DLL mid-install causes repeat failures; reinstall with it paused if needed. Mixing pip and conda pyarrow in one env is a classic way to get mismatched native libs; pick one installer.