@oscargus this will fail because of _contour_args in this line

x, y, z = self._contour_args(args, kwargs)

It'll need a check in that function too the if statements don't check non-zero len(args)
(Sorry, I was just about to raise a PR for this too)

Something like this should work (this will error out on no positional args, will need changes)

-       if nargs <= 2:
-           z = ma.asarray(args[0], dtype=np.float64)
-           x, y = self._initialize_x_y(z)
-           args = args[1:]
-       elif nargs <= 4:
-           x, y, z = self._check_xyz(args[:3], kwargs)
-           args = args[3:]
-       else:
-           raise _api.nargs_error(fn, takes="from 1 to 4", given=nargs)
+       if 0 < nargs <= 2:
+           z = ma.asarray(args[0], dtype=np.float64)
+           x, y = self._initialize_x_y(z)
+           args = args[1:]
+       elif 2 < nargs <= 4:
+           x, y, z = self._check_xyz(args[:3], kwargs)
+           args = args[3:]
+       else:
+           raise _api.nargs_error(fn, takes="from 1 to 4", given=nargs)

Though, I do have a question about allowing passing Z as a keyword argument or let it be a positional argument and error out if none are given? This is what the quiver PR also did.

Yeah, I noticed that as well (although it did work when running it interactively strangely enough). I was about to start extracting X, Y, and Z from the kwargs at some stage, but as this wasn't as quick as I thought I'll move this to draft for now. Feel free to prepare a better PR.

I think your fix, checking that there is at least one argument, is good to have anyway, but in the long run I think that X, Y, and Z should be extracted if kwargs (before that check).