def helper_clip(f, unit1, unit2, unit3):
# Treat the array being clipped as primary.
converters = [None]
if unit1 is None:
result_unit = dimensionless_unscaled
try:
converters += [(None if unit is None else
get_converter(unit, dimensionless_unscaled))
for unit in (unit2, unit3)]
except UnitsError:
raise UnitConversionError(
"Can only apply '{}' function to quantities with "
"compatible dimensions".format(f.__name__))
else:
result_unit = unit1
for unit in unit2, unit3:
try:
converter = get_converter(_d(unit), result_unit)
except UnitsError:
if unit is None:
# special case: OK if unitless number is zero, inf, nan
converters.append(False)
else:
raise UnitConversionError(
"Can only apply '{}' function to quantities with "
"compatible dimensions".format(f.__name__))
else:
converters.append(converter)
return converters, result_unit
def quantity(self, val):
val = u.Quantity(val)
try:
val.to(self.unit)
self.value = val.value
self.unit = val.unit
except UnitConversionError:
raise UnitConversionError(
"{0} parameter must have units homogeneous with {1}".format(
self.name, self.unit))
def get_converters_and_unit(f, unit1, unit2):
converters = [None, None]
# By default, we try adjusting unit2 to unit1, so that the result will
# be unit1 as well. But if there is no second unit, we have to try
# adjusting unit1 (to dimensionless, see below).
if unit2 is None:
if unit1 is None:
# No units for any input -- e.g., np.add(a1, a2, out=q)
return converters, dimensionless_unscaled
changeable = 0
# swap units.
unit2 = unit1
unit1 = None
elif unit2 is unit1:
# ensure identical units is fast ("==" is slow, so avoid that).
return converters, unit1
else:
changeable = 1
# Try to get a converter from unit2 to unit1.
if unit1 is None:
try:
converters[changeable] = get_converter(unit2,
dimensionless_unscaled)
except UnitsError:
# special case: would be OK if unitless number is zero, inf, nan
converters[1-changeable] = False
return converters, unit2
else:
return converters, dimensionless_unscaled
else:
try:
converters[changeable] = get_converter(unit2, unit1)
except UnitsError:
raise UnitConversionError(
"Can only apply '{0}' function to quantities "
"with compatible dimensions"
.format(f.__name__))
return converters, unit1
def converters_and_unit(function, method, *args):
"""Determine the required converters and the unit of the ufunc result.
Converters are functions required to convert to a ufunc's expected unit,
e.g., radian for np.sin; or to ensure units of two inputs are consistent,
e.g., for np.add. In these examples, the unit of the result would be
dimensionless_unscaled for np.sin, and the same consistent unit for np.add.
Parameters
----------
function : `~numpy.ufunc`
Numpy universal function
method : str
Method with which the function is evaluated, e.g.,
'__call__', 'reduce', etc.
*args : Quantity or other ndarray subclass
Input arguments to the function
Raises
------
TypeError : when the specified function cannot be used with Quantities
(e.g., np.logical_or), or when the routine does not know how to handle
the specified function (in which case an issue should be raised on
https://github.com/astropy/astropy).
UnitTypeError : when the conversion to the required (or consistent) units
is not possible.
"""
# Check whether we support this ufunc, by getting the helper function
# (defined in helpers) which returns a list of function(s) that convert the
# input(s) to the unit required for the ufunc, as well as the unit the
# result will have (a tuple of units if there are multiple outputs).
ufunc_helper = UFUNC_HELPERS[function]
if method == '__call__' or (method == 'outer' and function.nin == 2):
# Find out the units of the arguments passed to the ufunc; usually,
# at least one is a quantity, but for two-argument ufuncs, the second
# could also be a Numpy array, etc. These are given unit=None.
units = [getattr(arg, 'unit', None) for arg in args]
# Determine possible conversion functions, and the result unit.
converters, result_unit = ufunc_helper(function, *units)
if any(converter is False for converter in converters):
# for multi-argument ufuncs with a quantity and a non-quantity,
# the quantity normally needs to be dimensionless, *except*
# if the non-quantity can have arbitrary unit, i.e., when it
# is all zero, infinity or NaN. In that case, the non-quantity
# can just have the unit of the quantity
# (this allows, e.g., `q > 0.` independent of unit)
try:
# Don't fold this loop in the test above: this rare case
# should not make the common case slower.
for i, converter in enumerate(converters):
if converter is not False:
continue
if can_have_arbitrary_unit(args[i]):
converters[i] = None
else:
raise UnitConversionError(
"Can only apply '{}' function to "
"dimensionless quantities when other "
"argument is not a quantity (unless the "
"latter is all zero/infinity/nan)".format(
function.__name__))
except TypeError:
# _can_have_arbitrary_unit failed: arg could not be compared
# with zero or checked to be finite. Then, ufunc will fail too.
raise TypeError(
"Unsupported operand type(s) for ufunc {}: "
"'{}'".format(
function.__name__,
','.join([arg.__class__.__name__ for arg in args])))
# In the case of np.power and np.float_power, the unit itself needs to
# be modified by an amount that depends on one of the input values,
# so we need to treat this as a special case.
# TODO: find a better way to deal with this.
if result_unit is False:
if units[0] is None or units[0] == dimensionless_unscaled:
result_unit = dimensionless_unscaled
else:
if units[1] is None:
p = args[1]
else:
p = args[1].to(dimensionless_unscaled).value
try:
result_unit = units[0]**p
except ValueError as exc:
# Changing the unit does not work for, e.g., array-shaped
# power, but this is OK if we're (scaled) dimensionless.
try:
converters[0] = units[0]._get_converter(
dimensionless_unscaled)
except UnitConversionError:
raise exc
else:
result_unit = dimensionless_unscaled
else: # methods for which the unit should stay the same
nin = function.nin
unit = getattr(args[0], 'unit', None)
if method == 'at' and nin <= 2:
if nin == 1:
units = [unit]
else:
units = [unit, getattr(args[2], 'unit', None)]
converters, result_unit = ufunc_helper(function, *units)
# ensure there is no 'converter' for indices (2nd argument)
converters.insert(1, None)
elif method in {'reduce', 'accumulate', 'reduceat'} and nin == 2:
converters, result_unit = ufunc_helper(function, unit, unit)
converters = converters[:1]
if method == 'reduceat':
# add 'scale' for indices (2nd argument)
converters += [None]
else:
if method in {'reduce', 'accumulate', 'reduceat', 'outer'
} and nin != 2:
raise ValueError(
f"{method} only supported for binary functions")
raise TypeError(
"Unexpected ufunc method {}. If this should "
"work, please raise an issue on"
"https://github.com/astropy/astropy".format(method))
# for all but __call__ method, scaling is not allowed
if unit is not None and result_unit is None:
raise TypeError("Cannot use '{1}' method on ufunc {0} with a "
"Quantity instance as the result is not a "
"Quantity.".format(function.__name__, method))
if (converters[0] is not None
or (unit is not None and unit is not result_unit and
(not result_unit.is_equivalent(unit)
or result_unit.to(unit) != 1.))):
# NOTE: this cannot be the more logical UnitTypeError, since
# then things like np.cumprod will not longer fail (they check
# for TypeError).
raise UnitsError(
"Cannot use '{1}' method on ufunc {0} with a "
"Quantity instance as it would change the unit.".format(
function.__name__, method))
return converters, result_unit