def from_lal_unit(lunit):
"""Convert a LALUnit` into a `~astropy.units.Unit`
Parameters
----------
aunit : `LALUnit`
the input unit
Returns
-------
unit : `~astropy.units.Unit`
the Astropy representation of the input
Raises
------
ValueError
if Astropy doesn't understand the base units for the input
"""
try:
lunit = lal.Unit(lunit)
except RuntimeError:
raise TypeError("Cannot convert %r to lal.Unit" % lunit)
aunit = units.Unit("")
for power, lalbase in zip(lunit.unitNumerator, LAL_UNIT_INDEX):
# if not used, continue
if not power:
continue
# convert to astropy unit
try:
u = units.Unit(lal_unit_to_str(lalbase))
except ValueError:
raise ValueError("Astropy has no unit corresponding to %r" %
lalbase)
aunit *= u**power
return aunit
def to_lal_unit(aunit):
"""Convert the input unit into a `LALUnit`
For example::
>>> u = to_lal_unit('m**2 / kg ** 4')
>>> print(u)
m^2 kg^-4
Parameters
----------
aunit : `~astropy.units.Unit`, `str`
the input unit
Returns
-------
unit : `LALUnit`
the LALUnit representation of the input
Raises
------
ValueError
if LAL doesn't understand the base units for the input
"""
if isinstance(aunit, string_types):
aunit = units.Unit(aunit)
aunit = aunit.decompose()
lunit = lal.Unit()
for base, power in zip(aunit.bases, aunit.powers):
# try this base
try:
lalbase = LAL_UNIT_FROM_ASTROPY[base]
except KeyError:
lalbase = None
# otherwise loop through the equivalent bases
for eqbase in base.find_equivalent_units():
try:
lalbase = LAL_UNIT_FROM_ASTROPY[eqbase]
except KeyError:
continue
# if we didn't find anything, raise an exception
if lalbase is None:
raise ValueError("LAL has no unit corresponding to %r" % base)
lunit *= lalbase**power
return lunit