Uncertainties: Error Propagation Library

The `uncertainties` package is an open-source Python library for doing calculations on numbers that have uncertainties (like 3.14±0.01). It automatically propagates uncertainties and handles correlations using linear error propagation theory. Maintained by the lmfit organization, it is actively developed, with version 3.2.4 released in January 2026, and a major 4.0.0 release is forthcoming.