Source code for astropy.units.imperial

# Licensed under a 3-clause BSD style license - see LICENSE.rst

"""
This package defines colloquially used Imperial units.  They are
available in the `astropy.units.imperial` namespace, but not in the
top-level `astropy.units` namespace, e.g.::

    >>> import astropy.units as u
    >>> mph = u.imperial.mile / u.hour
    >>> mph
    Unit("mi / h")

To include them in `~astropy.units.UnitBase.compose` and the results of
`~astropy.units.UnitBase.find_equivalent_units`, do::

    >>> import astropy.units as u
    >>> u.imperial.enable()  # doctest: +SKIP
"""


from . import si
from .core import UnitBase, def_unit

_ns = globals()

###########################################################################
# LENGTH

def_unit(["inch"], 2.54 * si.cm, namespace=_ns, doc="International inch")
def_unit(["ft", "foot"], 12 * inch, namespace=_ns, doc="International foot")
def_unit(["yd", "yard"], 3 * ft, namespace=_ns, doc="International yard")
def_unit(["mi", "mile"], 5280 * ft, namespace=_ns, doc="International mile")
def_unit(["mil", "thou"], 0.001 * inch, namespace=_ns, doc="Thousandth of an inch")
def_unit(["nmi", "nauticalmile", "NM"], 1852 * si.m, namespace=_ns, doc="Nautical mile")
def_unit(["fur", "furlong"], 660 * ft, namespace=_ns, doc="Furlong")


###########################################################################
# AREAS

def_unit(["ac", "acre"], 43560 * ft**2, namespace=_ns, doc="International acre")


###########################################################################
# VOLUMES

def_unit(["gallon"], si.liter / 0.264172052, namespace=_ns, doc="U.S. liquid gallon")
def_unit(["quart"], gallon / 4, namespace=_ns, doc="U.S. liquid quart")
def_unit(["pint"], quart / 2, namespace=_ns, doc="U.S. liquid pint")
def_unit(["cup"], pint / 2, namespace=_ns, doc="U.S. customary cup")
def_unit(
    ["foz", "fluid_oz", "fluid_ounce"], cup / 8, namespace=_ns, doc="U.S. fluid ounce"
)
def_unit(
    ["tbsp", "tablespoon"], foz / 2, namespace=_ns, doc="U.S. customary tablespoon"
)
def_unit(["tsp", "teaspoon"], tbsp / 3, namespace=_ns, doc="U.S. customary teaspoon")


###########################################################################
# MASS

def_unit(
    ["oz", "ounce"],
    28.349523125 * si.g,
    namespace=_ns,
    doc="International avoirdupois ounce: mass",
)
def_unit(
    ["lb", "lbm", "pound"],
    16 * oz,
    namespace=_ns,
    doc="International avoirdupois pound: mass",
)
def_unit(
    ["st", "stone"], 14 * lb, namespace=_ns, doc="International avoirdupois stone: mass"
)
def_unit(["ton"], 2000 * lb, namespace=_ns, doc="International avoirdupois ton: mass")
def_unit(["slug"], 32.174049 * lb, namespace=_ns, doc="slug: mass")


###########################################################################
# SPEED

def_unit(
    ["kn", "kt", "knot", "NMPH"],
    nmi / si.h,
    namespace=_ns,
    doc="nautical unit of speed: 1 nmi per hour",
)


###########################################################################
# FORCE

def_unit("lbf", slug * ft * si.s**-2, namespace=_ns, doc="Pound: force")
def_unit(["kip", "kilopound"], 1000 * lbf, namespace=_ns, doc="Kilopound: force")


##########################################################################
# ENERGY

def_unit(["BTU", "btu"], 1.05505585 * si.kJ, namespace=_ns, doc="British thermal unit")
def_unit(
    ["cal", "calorie"],
    4.184 * si.J,
    namespace=_ns,
    doc="Thermochemical calorie: pre-SI metric unit of energy",
)
def_unit(
    ["kcal", "Cal", "Calorie", "kilocal", "kilocalorie"],
    1000 * cal,
    namespace=_ns,
    doc="Calorie: colloquial definition of Calorie",
)


##########################################################################
# PRESSURE

def_unit("psi", lbf * inch**-2, namespace=_ns, doc="Pound per square inch: pressure")


###########################################################################
# POWER

# Imperial units
def_unit(
    ["hp", "horsepower"],
    si.W / 0.00134102209,
    namespace=_ns,
    doc="Electrical horsepower",
)


###########################################################################
# TEMPERATURE

def_unit(
    ["deg_F", "Fahrenheit"],
    namespace=_ns,
    doc="Degrees Fahrenheit",
    format={"latex": r"{}^{\circ}F", "unicode": "°F"},
)
def_unit(
    ["deg_R", "Rankine"],
    namespace=_ns,
    doc="Rankine scale: absolute scale of thermodynamic temperature",
)


###########################################################################
# CLEANUP

del UnitBase
del def_unit


###########################################################################
# 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 Imperial units so they appear in results of
    `~astropy.units.UnitBase.find_equivalent_units` and
    `~astropy.units.UnitBase.compose`.

    This may be used with the ``with`` statement to enable Imperial
    units only temporarily.
    """
    # Local import to avoid cyclical import
    # Local import to avoid polluting namespace
    import inspect

    from .core import add_enabled_units

    return add_enabled_units(inspect.getmodule(enable))
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Source code for astropy.units.imperial
