# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
This package defines units used in the CDS format, both the units
defined in `Centre de Données astronomiques de Strasbourg
<http://cds.u-strasbg.fr/>`_ `Standards for Astronomical Catalogues 2.0
<http://cds.u-strasbg.fr/doc/catstd-3.2.htx>`_ format and the `complete
set of supported units <http://vizier.u-strasbg.fr/cgi-bin/Unit>`_.
This format is used by VOTable up to version 1.2.
These units are not available in the top-level `astropy.units`
namespace. To use these units, you must import the `astropy.units.cds`
module::
>>> from astropy.units import cds
>>> q = 10. * cds.lyr # doctest: +SKIP
To include them in `~astropy.units.UnitBase.compose` and the results of
`~astropy.units.UnitBase.find_equivalent_units`, do::
>>> from astropy.units import cds
>>> cds.enable() # doctest: +SKIP
"""
_ns = globals()
def _initialize_module():
# Local imports to avoid polluting top-level namespace
import numpy as np
from . import core
from astropy import units as u
from astropy.constants import si as _si
# The CDS format also supports power-of-2 prefixes as defined here:
# http://physics.nist.gov/cuu/Units/binary.html
prefixes = core.si_prefixes + core.binary_prefixes
# CDS only uses the short prefixes
prefixes = [(short, short, factor) for (short, long, factor) in prefixes]
# The following units are defined in alphabetical order, directly from
# here: http://vizier.u-strasbg.fr/cgi-bin/Unit
mapping = [
(['A'], u.A, "Ampere"),
(['a'], u.a, "year", ['P']),
(['a0'], _si.a0, "Bohr radius"),
(['al'], u.lyr, "Light year", ['c', 'd']),
(['lyr'], u.lyr, "Light year"),
(['alpha'], _si.alpha, "Fine structure constant"),
((['AA', 'Å'], ['Angstrom', 'Angstroem']), u.AA, "Angstrom"),
(['arcmin', 'arcm'], u.arcminute, "minute of arc"),
(['arcsec', 'arcs'], u.arcsecond, "second of arc"),
(['atm'], _si.atm, "atmosphere"),
(['AU', 'au'], u.au, "astronomical unit"),
(['bar'], u.bar, "bar"),
(['barn'], u.barn, "barn"),
(['bit'], u.bit, "bit"),
(['byte'], u.byte, "byte"),
(['C'], u.C, "Coulomb"),
(['c'], _si.c, "speed of light", ['p']),
(['cal'], 4.1854 * u.J, "calorie"),
(['cd'], u.cd, "candela"),
(['ct'], u.ct, "count"),
(['D'], u.D, "Debye (dipole)"),
(['d'], u.d, "Julian day", ['c']),
((['deg', '°'], ['degree']), u.degree, "degree"),
(['dyn'], u.dyn, "dyne"),
(['e'], _si.e, "electron charge", ['m']),
(['eps0'], _si.eps0, "electric constant"),
(['erg'], u.erg, "erg"),
(['eV'], u.eV, "electron volt"),
(['F'], u.F, "Farad"),
(['G'], _si.G, "Gravitation constant"),
(['g'], u.g, "gram"),
(['gauss'], u.G, "Gauss"),
(['geoMass', 'Mgeo'], u.M_earth, "Earth mass"),
(['H'], u.H, "Henry"),
(['h'], u.h, "hour", ['p']),
(['hr'], u.h, "hour"),
(['\\h'], _si.h, "Planck constant"),
(['Hz'], u.Hz, "Hertz"),
(['inch'], 0.0254 * u.m, "inch"),
(['J'], u.J, "Joule"),
(['JD'], u.d, "Julian day", ['M']),
(['jovMass', 'Mjup'], u.M_jup, "Jupiter mass"),
(['Jy'], u.Jy, "Jansky"),
(['K'], u.K, "Kelvin"),
(['k'], _si.k_B, "Boltzmann"),
(['l'], u.l, "litre", ['a']),
(['lm'], u.lm, "lumen"),
(['Lsun', 'solLum'], u.solLum, "solar luminosity"),
(['lx'], u.lx, "lux"),
(['m'], u.m, "meter"),
(['mag'], u.mag, "magnitude"),
(['me'], _si.m_e, "electron mass"),
(['min'], u.minute, "minute"),
(['MJD'], u.d, "Julian day"),
(['mmHg'], 133.322387415 * u.Pa, "millimeter of mercury"),
(['mol'], u.mol, "mole"),
(['mp'], _si.m_p, "proton mass"),
(['Msun', 'solMass'], u.solMass, "solar mass"),
((['mu0', 'µ0'], []), _si.mu0, "magnetic constant"),
(['muB'], _si.muB, "Bohr magneton"),
(['N'], u.N, "Newton"),
(['Ohm'], u.Ohm, "Ohm"),
(['Pa'], u.Pa, "Pascal"),
(['pc'], u.pc, "parsec"),
(['ph'], u.ph, "photon"),
(['pi'], u.Unit(np.pi), "π"),
(['pix'], u.pix, "pixel"),
(['ppm'], u.Unit(1e-6), "parts per million"),
(['R'], _si.R, "gas constant"),
(['rad'], u.radian, "radian"),
(['Rgeo'], _si.R_earth, "Earth equatorial radius"),
(['Rjup'], _si.R_jup, "Jupiter equatorial radius"),
(['Rsun', 'solRad'], u.solRad, "solar radius"),
(['Ry'], u.Ry, "Rydberg"),
(['S'], u.S, "Siemens"),
(['s', 'sec'], u.s, "second"),
(['sr'], u.sr, "steradian"),
(['Sun'], u.Sun, "solar unit"),
(['T'], u.T, "Tesla"),
(['t'], 1e3 * u.kg, "metric tonne", ['c']),
(['u'], _si.u, "atomic mass", ['da', 'a']),
(['V'], u.V, "Volt"),
(['W'], u.W, "Watt"),
(['Wb'], u.Wb, "Weber"),
(['yr'], u.a, "year"),
]
for entry in mapping:
if len(entry) == 3:
names, unit, doc = entry
excludes = []
else:
names, unit, doc, excludes = entry
core.def_unit(names, unit, prefixes=prefixes, namespace=_ns, doc=doc,
exclude_prefixes=excludes)
core.def_unit(['µas'], u.microarcsecond,
doc="microsecond of arc", namespace=_ns)
core.def_unit(['mas'], u.milliarcsecond,
doc="millisecond of arc", namespace=_ns)
core.def_unit(['---'], u.dimensionless_unscaled,
doc="dimensionless and unscaled", namespace=_ns)
core.def_unit(['%'], u.percent,
doc="percent", namespace=_ns)
# The Vizier "standard" defines this in units of "kg s-3", but
# that may not make a whole lot of sense, so here we just define
# it as its own new disconnected unit.
core.def_unit(['Crab'], prefixes=prefixes, namespace=_ns,
doc="Crab (X-ray) flux")
_initialize_module()
###########################################################################
# DOCSTRING
# This generates a docstring for this module that describes all of the
# standard units defined here.
from .utils import generate_unit_summary as _generate_unit_summary
if __doc__ is not None:
__doc__ += _generate_unit_summary(globals())
[docs]def enable():
"""
Enable CDS units so they appear in results of
`~astropy.units.UnitBase.find_equivalent_units` and
`~astropy.units.UnitBase.compose`. This will disable
all of the "default" `astropy.units` units, since there
are some namespace clashes between the two.
This may be used with the ``with`` statement to enable CDS
units only temporarily.
"""
# Local import to avoid cyclical import
from .core import set_enabled_units
# Local import to avoid polluting namespace
import inspect
return set_enabled_units(inspect.getmodule(enable))