erfa.p2s does not accept units except for distance #16873
Description
Description
In liberfa/pyerfa#149, @maxnoe reported the following error, which had him puzzled (transferred here since astropy.units.quantity_helpers.erfa is responsible for making pyerfa work with units).
from erfa.ufunc import s2p as spherical_to_cartesian
import astropy.units as u
import numpy as np
lon = np.pi / 2
lat = np.pi / 4
spherical_to_cartesian(lon, lat, 5 * u.km)results in this relatively unhelpful error:
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
Cell In[3], line 8
5 lon = np.pi / 2
6 lat = np.pi / 4
----> 8 spherical_to_cartesian(lon, lat, 5 * u.km)
File ~/.local/conda/envs/cta-dev/lib/python3.11/site-packages/astropy/units/quantity.py:691, in Quantity.__array_ufunc__(self, function, method, *inputs, **kwargs)
689 return NotImplemented
690 else:
--> 691 raise e
File ~/.local/conda/envs/cta-dev/lib/python3.11/site-packages/astropy/units/quantity.py:636, in Quantity.__array_ufunc__(self, function, method, *inputs, **kwargs)
631 # Determine required conversion functions -- to bring the unit of the
632 # input to that expected (e.g., radian for np.sin), or to get
633 # consistent units between two inputs (e.g., in np.add) --
634 # and the unit of the result (or tuple of units for nout > 1).
635 try:
--> 636 converters, unit = converters_and_unit(function, method, *inputs)
638 out = kwargs.get("out", None)
639 # Avoid loop back by turning any Quantity output into array views.
File ~/.local/conda/envs/cta-dev/lib/python3.11/site-packages/astropy/units/quantity_helper/converters.py:181, in converters_and_unit(function, method, *args)
178 units = [getattr(arg, "unit", None) for arg in args]
180 # Determine possible conversion functions, and the result unit.
--> 181 converters, result_unit = ufunc_helper(function, *units)
183 if any(converter is False for converter in converters):
184 # for multi-argument ufuncs with a quantity and a non-quantity,
185 # the quantity normally needs to be dimensionless, *except*
(...)
188 # can just have the unit of the quantity
189 # (this allows, e.g., `q > 0.` independent of unit)
190 try:
191 # Don't fold this loop in the test above: this rare case
192 # should not make the common case slower.
File ~/.local/conda/envs/cta-dev/lib/python3.11/site-packages/astropy/units/quantity_helper/erfa.py:70, in helper_s2p(f, unit1, unit2, unit3)
67 from astropy.units.si import radian
69 try:
---> 70 return [get_converter(unit1, radian), get_converter(unit2, radian), None], unit3
71 except UnitsError:
72 raise UnitTypeError(
73 f"Can only apply '{f.__name__}' function to quantities with angle units"
74 )
File ~/.local/conda/envs/cta-dev/lib/python3.11/site-packages/astropy/units/quantity_helper/helpers.py:42, in get_converter(from_unit, to_unit)
38 def get_converter(from_unit, to_unit):
39 """Like Unit._get_converter, except returns None if no scaling is needed,
40 i.e., if the inferred scale is unity.
41 """
---> 42 converter = from_unit._get_converter(to_unit)
43 return None if converter is unit_scale_converter else converter
AttributeError: 'NoneType' object has no attribute '_get_converter'
Expected behavior
No response
How to Reproduce
No response
Versions
import astropy
try:
astropy.system_info()
except AttributeError:
import platform; print(platform.platform())
import sys; print("Python", sys.version)
import astropy; print("astropy", astropy.__version__)
import numpy; print("Numpy", numpy.__version__)
import erfa; print("pyerfa", erfa.__version__)
try:
import scipy
print("Scipy", scipy.__version__)
except ImportError:
print("Scipy not installed")
try:
import matplotlib
print("Matplotlib", matplotlib.__version__)
except ImportError:
print("Matplotlib not installed")# Paste the result here