ImportError: C extension: No module named 'pandas._libs.tslibs.conversion' not built

How to fix ImportError: C extension: No module named 'pandas._libs.tslibs.conversion' not built

You are importing pandas from a source checkout whose C extensions were never built. Either build them or just install a binary wheel with pip. Most people hitting this should do the pip reinstall: the error only appears when a source directory shadows a working install.

The exact error

ImportError: C extension: No module named 'pandas._libs.tslibs.conversion' not built

Fix it

1. Check whether you are inside the pandas source dir: pwd and look for setup.py. If yes, cd out.

Expected: you know whether the source tree is shadowing the install

1. Simplest fix: python -m pip install --force-reinstall pandas.

Expected: python -c "import pandas; print(pandas.__version__)" works from any directory

1. If you actually develop pandas: build the extensions in place, then import again.

Expected: the C extensions build and import succeeds

When this applies

import pandas raises the 'C extension ... not built' ImportError naming a pandas._libs module

When this does NOT apply

plain No module named 'pandas' or a missing optional dependency like openpyxl

Versions

pandas built from source / dev installs, any version

Why it happens

pandas ships compiled Cython extensions. A source checkout (or a copied pandas folder) without built extensions cannot import.

Edge cases

Do not run your scripts from inside the pandas repo directory; the local pandas/ folder shadows site-packages.