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# Source code for astropy.units.cds

    # 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://vizier.u-strasbg.fr/vizier/doc/catstd-3.2.htx>`_ format and the `complete
    set of supported units <https://vizier.u-strasbg.fr/viz-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():
        """Initialize CDS units module."""

        # Local imports to avoid polluting top-level namespace
        import numpy as np

        from astropy import units as u
        from astropy.constants import si as _si

        from . import core

        # 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: https://vizier.u-strasbg.fr/viz-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())

    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 imports to avoid cyclical import and polluting namespace
        import inspect

        from .core import set_enabled_units

        return set_enabled_units(inspect.getmodule(enable))