Dataset.eval does not support N-dimensional objects with N > 2 #11062
Description
What is your issue?
Using
- xarray 2025.12.0
- pandas 2.3.3
Dataset.eval uses Pandas under the hood to handle the eval of arbitrary expressions
Lines 9538 to 9598 in f8bc4f4
However, Pandas explicitly does not support data with dimensionality > 2:
Since I was interested in simple additions and subtractions among variables, I tried to disable the check. The code runs on benchmark 3D data, but painstakingly slowly.
I came up with this solution
def _ds_eval(ds: xr.Dataset, expr: str) -> xr.DataArray:
import ast
ALLOWED_NODES = (
ast.Expression, ast.BinOp, ast.Name, ast.Load, ast.Constant,
ast.Add, ast.Sub, ast.Mult, ast.Div,
)
def validate(expr):
tree = ast.parse(expr, mode="eval")
for node in ast.walk(tree):
if not isinstance(node, ALLOWED_NODES):
raise ValueError(f"Disallowed expression: {node}")
return tree
tree = validate(expr)
compiled = compile(tree, "<expr>", "eval")
return eval(
compiled,
{"__builtins__": {}}, # globals
ds.data_vars, # locals
)
# example usage, assuming ds has variables x and y
z = ds_eval(ds, "x + y")Since ds.eval is read-only, it is not possible to monkeypatch the Dataset object.
I'm putting it here in case someone else needs it and to open a discussion on possible improvements on the current implementation, which I would be happy to help on.