Custom registry class
Custom registry class#
Pay as you go#
Pint registry functionality is divided into facets. The default UnitRegistry inherits from all of them, providing a full fledged and feature rich registry. However, in certain cases you might want to have a simpler and lighter registry. Just pick what you need and create your own.
FormattingRegistry: adds the capability to format quantities and units into string.
SystemRegistry: adds the capability to work with system of units.
GroupRegistry: adds the capability to group units.
MeasurementRegistry: adds the capability to handle measurements (quantities with uncertainties).
NumpyRegistry: adds the capability to interoperate with NumPy.
DaskRegistry: adds the capability to interoperate with Dask.
ContextRegistry: the capability to contexts: predefined conversions between incompatible dimensions.
NonMultiplicativeRegistry: adds the capability to handle nonmultiplicative units (offset, logarithmic).
PlainRegistry: base implementation for registry, units and quantities.
The only required one is PlainRegistry, the rest are completely optional.
>>> import pint >>> class MyRegistry(pint.facets.NonMultiplicativeRegistry): ... pass
NonMultiplicativeRegistry is a subclass from PlainRegistry, and therefore it is not required to add it explicitly to MyRegistry bases.
You can add some specific functionality to your new registry.
>>> import pint >>> class MyRegistry(pint.UnitRegistry): ... ... def my_specific_function(self): ... """Do something ... """
Custom Quantity and Unit class#
You can also create your own Quantity and Unit class, you must derive from Quantity (or Unit) and tell your registry about it.
For example, if you want to create a new UnitRegistry subclass you need to derive the Quantity and Unit classes from it.
>>> import pint >>> class MyQuantity(pint.UnitRegistry.Quantity): ... ... # Notice that subclassing pint.Quantity ... # is not necessary. ... # Pint will inspect the Registry class and create ... # a Quantity class that contains all the ... # required parents. ... ... def to_my_desired_format(self): ... """Do something else ... """ ... >>> class MyUnit(pint.UnitRegistry.Unit): ... ... # Notice that subclassing pint.Quantity ... # is not necessary. ... # Pint will inspect the Registry class and create ... # a Quantity class that contains all the ... # required parents. ... ... def to_my_desired_format(self): ... """Do something else ... """
Then, you need to create a custom registry but deriving from GenericUnitRegistry so you can specify the types of
>>> from typing_extensions import TypeAlias # Python 3.9 >>> # from typing import TypeAlias # Python 3.10+ >>> class MyRegistry(pint.registry.GenericUnitRegistry[MyQuantity, pint.Unit]): ... ... Quantity: TypeAlias = MyQuantity ... Unit: TypeAlias = MyUnit ...
While these examples demonstrate how to add functionality to the default registry class, you can actually subclass just the PlainRegistry, and GenericPlainRegistry.