DimensionlessUnitSystem

class gala.units.DimensionlessUnitSystem

Bases: UnitSystem

Initialize a dimensionless unit system. All quantities are treated as dimensionless.

Methods Summary

decompose(q)	A thin wrapper around astropy.units.Quantity.decompose() that knows how to handle Quantities with physical types with non-default representations.
from_string(name)	Create a UnitSystem instance from a name.
get_constant(name)	Retrieve a constant with specified name in this unit system.
to_dict()	Return a dictionary representation of the unit system with keys set by the physical types and values set by the unit objects.

Methods Documentation

decompose(q)

A thin wrapper around astropy.units.Quantity.decompose() that knows how to handle Quantities with physical types with non-default representations.

Parameters:

qQuantity

An instance of an astropy Quantity object.

Returns:

qQuantity

A new quantity, decomposed to be represented in this unit system.

classmethod from_string(name: str) → UnitSystem

Create a UnitSystem instance from a name.

Parameters:

namestr

The name of the unit system. Examples of valid names are ‘galactic’, ‘solarsystem’, and ‘dimensionless’.

Returns:

usysUnitSystem

The corresponding unit system instance.

Examples

Create the galactic unit system from its name:

>>> usys = UnitSystem.from_string('galactic')
>>> usys['length']
Unit("kpc")

get_constant(name)

Retrieve a constant with specified name in this unit system.

Parameters:

namestr

The name of the constant, e.g., G.

Returns:

constfloat

The value of the constant represented in this unit system.

Examples

We will get the value of the speed of light in a custom unit system:

>>> usys = UnitSystem(u.kpc, u.Myr, u.Msun, u.radian)
>>> usys.get_constant('c')
306.6013937855506

to_dict()

Return a dictionary representation of the unit system with keys set by the physical types and values set by the unit objects.