Source code for astropy.units.physical

# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICENSE.rst

"""
Defines physical unit names.

This module is not intended for use by user code directly.  Instead,
the physical unit name of a `Unit` can be obtained using its `ptype`
property.
"""


from . import core
from . import si
from . import astrophys
from . import cgs
from . import imperial


__all__ = ['def_physical_type', 'get_physical_type']


_physical_unit_mapping = {}
_unit_physical_mapping = {}


[docs]def def_physical_type(unit, name): """ Adds a new physical unit mapping. Parameters ---------- unit : `~astropy.units.UnitBase` instance The unit to map from. name : str The physical name of the unit. """ r = unit._get_physical_type_id() if r in _physical_unit_mapping: raise ValueError( "{!r} ({!r}) already defined as {!r}".format( r, name, _physical_unit_mapping[r])) _physical_unit_mapping[r] = name _unit_physical_mapping[name] = r
[docs]def get_physical_type(unit): """ Given a unit, returns the name of the physical quantity it represents. If it represents an unknown physical quantity, ``"unknown"`` is returned. Parameters ---------- unit : `~astropy.units.UnitBase` instance The unit to lookup Returns ------- physical : str The name of the physical quantity, or unknown if not known. """ r = unit._get_physical_type_id() return _physical_unit_mapping.get(r, 'unknown')
for unit, name in [ (core.Unit(1), 'dimensionless'), (si.m, 'length'), (si.m ** 2, 'area'), (si.m ** 3, 'volume'), (si.s, 'time'), (si.rad, 'angle'), (si.sr, 'solid angle'), (si.m / si.s, 'speed'), (si.m / si.s ** 2, 'acceleration'), (si.Hz, 'frequency'), (si.g, 'mass'), (si.mol, 'amount of substance'), (si.K, 'temperature'), (si.deg_C, 'temperature'), (imperial.deg_F, 'temperature'), (si.N, 'force'), (si.J, 'energy'), (si.Pa, 'pressure'), (si.W, 'power'), (si.kg / si.m ** 3, 'mass density'), (si.m ** 3 / si.kg, 'specific volume'), (si.mol / si.m ** 3, 'molar volume'), (si.kg * si.m / si.s, 'momentum/impulse'), (si.kg * si.m ** 2 / si.s, 'angular momentum'), (si.rad / si.s, 'angular speed'), (si.rad / si.s ** 2, 'angular acceleration'), (si.g / (si.m * si.s), 'dynamic viscosity'), (si.m ** 2 / si.s, 'kinematic viscosity'), (si.m ** -1, 'wavenumber'), (si.A, 'electrical current'), (si.C, 'electrical charge'), (si.V, 'electrical potential'), (si.Ohm, 'electrical resistance'), (si.S, 'electrical conductance'), (si.F, 'electrical capacitance'), (si.C * si.m, 'electrical dipole moment'), (si.A / si.m ** 2, 'electrical current density'), (si.V / si.m, 'electrical field strength'), (si.C / si.m ** 2, 'electrical flux density'), (si.C / si.m ** 3, 'electrical charge density'), (si.F / si.m, 'permittivity'), (si.Wb, 'magnetic flux'), (si.T, 'magnetic flux density'), (si.A / si.m, 'magnetic field strength'), (si.H / si.m, 'electromagnetic field strength'), (si.H, 'inductance'), (si.cd, 'luminous intensity'), (si.lm, 'luminous flux'), (si.lx, 'luminous emittance/illuminance'), (si.W / si.sr, 'radiant intensity'), (si.cd / si.m ** 2, 'luminance'), (astrophys.Jy, 'spectral flux density'), (cgs.erg / si.angstrom / si.cm ** 2 / si.s, 'spectral flux density wav'), (astrophys.photon / si.Hz / si.cm ** 2 / si.s, 'photon flux density'), (astrophys.photon / si.AA / si.cm ** 2 / si.s, 'photon flux density wav'), (astrophys.R, 'photon flux'), (astrophys.bit, 'data quantity'), (astrophys.bit / si.s, 'bandwidth'), (cgs.Franklin, 'electrical charge (ESU)'), (cgs.statampere, 'electrical current (ESU)'), (cgs.Biot, 'electrical current (EMU)'), (cgs.abcoulomb, 'electrical charge (EMU)') ]: def_physical_type(unit, name)