Slight rearrangement of PairGrid variable processing

seaborn/axisgrid.py

@@ -1161,20 +1161,20 @@ def __init__(
         if y_vars is None:
             y_vars = numeric_cols
 
-        if not len(x_vars):
-            raise ValueError("No numeric variables found in for grid columns.")
-        if not len(y_vars):
-            raise ValueError("No numeric variables found for grid rows.")
-
         if np.isscalar(x_vars):
             x_vars = [x_vars]
         if np.isscalar(y_vars):
             y_vars = [y_vars]
 
-        self.x_vars = list(x_vars)
-        self.y_vars = list(y_vars)
+        self.x_vars = x_vars = list(x_vars)
+        self.y_vars = y_vars = list(y_vars)
         self.square_grid = self.x_vars == self.y_vars
 
+        if not x_vars:
+            raise ValueError("No variables found for grid columns.")
+        if not y_vars:
+            raise ValueError("No variables found for grid rows.")
+
         # Create the figure and the array of subplots
         figsize = len(x_vars) * height * aspect, len(y_vars) * height
 

seaborn/tests/test_axisgrid.py

@@ -757,7 +757,7 @@ def test_size(self):
 
     def test_empty_grid(self):
 
-        with pytest.raises(ValueError, match="No numeric variables"):
+        with pytest.raises(ValueError, match="No variables found"):
             ag.PairGrid(self.df[["a", "b"]])
 
     def test_map(self):