Divergence and Vorticity Dx/Dy creates TypeError: too many positional arguments

[chasecalkins]

Linux
Python 3.8.10

import metpy; print(metpy.__version__)

1.1.0

lat = (np.arange(0,121)*.25)+20
lat = lat[::-1]
lon = (np.arange(0,261)*.25)+230
...
dx,dy = mpcalc.lat_lon_grid_deltas(lon,lat)
GRN = mpcalc.gradient_richardson_number( GPM * units('meter'), thta, u_wind*units('m/s'), v_wind*units('m/s') )
fronto = mpcalc.frontogenesis(thta, u_wind*units('m/s'), v_wind*units('m/s'), dx, dy)
divergence  =  mpcalc.divergence(u_wind, v_wind)  # (or setting dx/dy = None)

    divergence  =  mpcalc.divergence(u_wind, v_wind)
  File "/home/ccalkins/.local/lib/python3.8/site-packages/metpy/xarray.py", line 1506, in wrapper
    raise ValueError('Must provide dx/dy arguments or input DataArray with '
ValueError: Must provide dx/dy arguments or input DataArray with latitude/longitude coordinates.

As it is should, however... adding in the dx/dy

divergence  =  mpcalc.divergence(u_wind, v_wind, dx, dy)

    divergence  =  mpcalc.divergence(u_wind, v_wind, dx, dy)
  File "/home/ccalkins/.local/lib/python3.8/site-packages/metpy/xarray.py", line 1435, in wrapper
    bound_args = signature(func).bind(*args, **kwargs)
  File "/usr/lib/python3.8/inspect.py", line 3037, in bind
    return self._bind(args, kwargs)
  File "/usr/lib/python3.8/inspect.py", line 2963, in _bind
    raise TypeError(
TypeError: too many positional arguments

Is there a issue in how I'm inputting the parameters? In the https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.divergence.html#divergence, theres a * for a parameter, so I'm not sure what this * is referring to, if anything? This also seems to be an issue on vorticity as well.

On https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.html#module-metpy.calc it list divergence and vorticity as

divergence(u, v, *[, dx, dy, x_dim, y_dim])	Calculate the horizontal divergence of a vector.

vorticity(u, v, *[, dx, dy, x_dim, y_dim])	Calculate the vertical vorticity of the horizontal wind.

But on others,

total_deformation(u, v[, dx, dy, x_dim, y_dim])	Calculate the horizontal total deformation of the horizontal wind.

shearing_deformation(u, v[, dx, dy, x_dim, …])	Calculate the shearing deformation of the horizontal wind.

stretching_deformation(u, v[, dx, dy, …])	Calculate the stretching deformation of the horizontal wind.

I've tried these other 3 and they all work as they should so I'm just curious what the issue is on the divergence and vorticity?

-Chase

[jthielen]

divergence, vorticity, and advection have their "grid parameters" specified as keyword-only arguments to be able to most flexibly handle varying dimensions (see #1519 for reasoning). This is what that * in the signature means...everything after that * is a keyword-only argument. In your code, this will look like

divergence = mpcalc.divergence(u_wind, v_wind, dx=dx, dy=dy)

[KCorb11]

This thread is helpful, but vorticity and advection are behaving in different ways for me. absolute vorticity is fine with the following:

avor_500 = mpcalc.absolute_vorticity(ug_500, vg_500, dx, dy, lat2d_for_coriolis)

but advection will not work the same way. I need to have dx=dx and dy=dy.

adv_500 = mpcalc.advection(avor_500, ug_500, vg_500, dx=dx, dy=dy) * 1e9

I'm trying to understand why for an assignment for my class.

Thanks!

Update: Now I see that vorticity and absolute vorticity are not the same in terms of positional versus keywords; i.e., the *. I think they really should be!