Overview

Unitty (pronounced ‘unity’) let’s you switch between units and unit systems with no fuss. It’s based on a phiolosophy that:

• Units are useful for inputs
• Units are useful for outputs (e.g. reports, plots)
• Calculations are done in SI units, so units are not needed unless checking.
• Unittests are used to encompass dimensional checks. Dimensional checks themselves are insufficient.
• Quantities are named adequately in the code (e.g. ‘area’, ‘length’, ‘mass’). The kind of quantity they represent is clear from their names, and so representing it elsewhere is typically redundant.

Unitty provides a flexible, lightweight package to:

• Automatically switch outputs to a different unit system using a single command, while keeping meaningful units (e.g. for force, pressure, etc.). This capability was a core reason to write unitty.
• Apply units intuitively.
• Convert numbers to and from different units.
• Fully customise units and unit systems. The user needs full flexibility of the systems and units used.
• Bundle values with units into quantities for downstream use (e.g. reports, plots).
• Not lock the user into objects with units attached. By default, units are not attached to calculation objects - the results are simply floats or arrays. This behaviour can be changed automatically to do dimensional checks during unittesting.
• Use meaningful units (e.g. for force, pressure, etc.) while also allowing dimensionality reduction and checking. Automatic dimensionality reduction in some other packages can be frustrating.

It is built on the idea that units provide scale factors to convert numbers to and from values in SI base units. Since SI base units all have magnitudes of 1.0, unit information need not be in the calculations themselves.