keyword parameter t in galpy.orbit.Orbits.Orbit._call_internal will be ignored in some cases

[azz147]

🐛 Bug

The below line will cause that passing single keyword parameter t will be ignored because len(args)==0 is true in that case

galpy/galpy/orbit/Orbits.py

Line 4858 in 861c2f7

if len(args) == 0 or (not hasattr(self,'t') and args[0] == 0. ):

Reproducible example

from astropy import units
from galpy.potential import MWPotential2014, ChandrasekharDynamicalFrictionForce
from galpy.orbit import Orbit
import numpy
o= Orbit.from_name('LMC')
ts= numpy.linspace(0.,-10.,1001)*units.Gyr
o.integrate(ts,MWPotential2014)
print(o.SkyCoord(t=0).ra ,o.SkyCoord(t=-100).ra)
# 78d46m12s 78d46m12s
print(o.SkyCoord(0).ra,o.SkyCoord(-100).ra)
# 78d46m12s 174d18m00.10529969s

Expected behavior

I expect the below lines should have the same output or the document states the t parameter will be ignored in this case.

print(o.SkyCoord(t=0).ra ,o.SkyCoord(t=-100).ra)
print(o.SkyCoord(0).ra,o.SkyCoord(-100).ra)

[jobovy]

Yes, it's true that this doesn't work. Perhaps the documentation could be clearer, but t is supposed to be given as an argument, not a keyword argument:

https://docs.galpy.org/en/latest/reference/orbitskycoord.html

A quick fix would be to insert

if len(args) == 0 and 't' in kwargs:
    args= [kwargs.get('t')]

just before

galpy/galpy/orbit/Orbits.py

Line 4858 in 861c2f7

if len(args) == 0 or (not hasattr(self,'t') and args[0] == 0. ):

Care to open a PR? Would also need a test in tests/test_orbit.py.

[azz147]

Sorry for the late reply. I've created a PR #569 about this.
I use args= [kwargs.pop('t')] to mimic the case where t is passed as args.

I tried to run all the tests in tests/test_orbit.py but it seems even with the unchanged code some tests still fail. I am not sure whether this is expected.

For example, use commit d6234fd and run

python -m pytest -v tests/test_orbit.py::test_physical_output

I will get

FAILED tests/test_orbit.py::test_physical_output - AttributeError: 'Orbit' object has no attribute '_aA_Or'

[jobovy]

Thanks, the PR looks good!

Don't worry about that error, I think it's unrelated to the change (and all the CI tests pass). I think I've encountered this locally before as well and don't quite remember what the issue was. I think it might be that you don't have the C extensions compiled and then the actionAngle method used in that test falls back onto a Python version that does not have all features, resulting in missing attributes.