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| -rw-r--r-- | mdpoly/state.py | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/mdpoly/state.py b/mdpoly/state.py index 001d9b6..f22d502 100644 --- a/mdpoly/state.py +++ b/mdpoly/state.py @@ -22,6 +22,10 @@ class State: def index(self, var: Var) -> Index: """ Get the index for a variable. """ + from .leaves import Var + if not isinstance(var, Var): + raise IndexError(f"Only variables (type {Var}) can be indexed.") + if var not in self.variables.keys(): new_index = self._make_index() self.variables[var] = new_index |