v2.21

• Remove % from tight_units list.
• Add spacer keyword argument to Quantity.render, Quantity.fixed and Quantity.binary.
• Add support for scaling with binary scale factors.
• Add USD and bps unit conversions
• Add support # modifier to f & g formats
• Add transparent_preferences Quantity attribute.

v2.20

• Include full quantities if available in IncompatibleUnits errors

v2.19

• Added new standard SI scale factors (Q, R, r, q).
• Subclasses of Quantity with units now convert values to the desired units rather than allowing the units of the class to be overridden by those of the value.
• Added scale factor conversion.
• Added quantity functions: as_real, as_tuple, render, fixed, and binary.
• Fixed rendering of full precision numbers in Quantity.fixed().
• Added preferred_units Quantity preference.
• Added “cover” option to strip_radix Quantity preference.
• Added type hints.

v2.18

• Support parameterized unit conversions (such as molarity).
• Allow % to act as a scale factor.
• First argument of scaling functions are now guaranteed to be quantities.
• Added UnitConversion.fixture decorator function.
• Added UnitConversion.activate method (allows overridden converters to be re-activated).

2.17

• Refine the list of currency symbols.
• Allows currency symbols to be given before or after the underlying number.
• Allow Quantity subclasses to be used in scaling if they have units.

v2.16

• Add support for — as comment character and make it the default.

v2.15

• Updated predefined physical constants to CODATA 2018 values.
• Switched to more permissive MIT license.
• Add feet to the available length/distance unit conversions.

v2.14

• Allow primary argument of Quantity.is_close() and Quantity.add() to be a string.

v2.13

• Allow currency symbols in compound units (ex: $/oz or lbs/$).

v2.12

• Allow currency symbols in compound units (ex: $/oz or lbs/$).