Support derivation of only variable graph_inputs

Author: Dhruvanshu-Joshi

pytensor/graph/basic.py

@@ -938,58 +938,50 @@ def graph_inputs(
 
 def required_graph_inputs(
     graph: Variable[Any, Any] | Iterable[Variable[Any, Any]],
-) -> list[Variable[Any, Any]]:
+) -> Generator[Variable, None, None]:
     """
     Get the inputs into PyTensor variables
 
     Parameters
     ----------
-        graph: PyTensor `Variable` instances
+    graph: PyTensor `Variable` instances
         Output `Variable` instances from which to search backward through
         owners.
 
     Returns
     -------
-        List of tensor variables that are input nodes with no owner, in the order
+        Tensor variables that are input nodes with no owner, in the order
         found by a left-recursive depth-first search started at the nodes in `graphs`.
 
     Examples
     --------
-    >>> import pytensor as pt
-    >>> x=pt.vector('x')
-    >>> y=pt.constant('y')
-    >>> z = pt.mul(x*y)
-    >>> required_graph_inputs([a])
-    [[[ 0  1  2  3]
-      [ 4  5  6  7]
-      [ 8  9 10 11]]
-
-     [[12 13 14 15]
-      [16 17 18 19]
-      [20 21 22 23]]]
-
-
-    >>> pt.matrix_transpose(x).eval()
-    [[[ 0  4  8]
-      [ 1  5  9]
-      [ 2  6 10]
-      [ 3  7 11]]
-
-     [[12 16 20]
-      [13 17 21]
-      [14 18 22]
-      [15 19 23]]]
+
+    .. code-block:: python
+
+        import pytensor
+        import pytensor.tensor as pt
+
+        x = pt.vector('x')
+        y = pt.constant(2)
+        z = pt.mul(x*y)
+
+        pytensor.dprint(graph_inputs([z]))
+        # x [id A]
+        # 2 [id B]
+
+        pytensor.dprint(required_graph_inputs([z]))
+        # x [id A]
     """
     from pytensor.compile.sharedvalue import SharedVariable
 
     if isinstance(graph, Variable):
         graph = [graph]
 
-    return [
+    return (
         v
         for v in graph_inputs(graph)
         if isinstance(v, Variable) and not isinstance(v, Constant | SharedVariable)
-    ]
+    )
 
 
 def vars_between(

tests/graph/test_basic.py

@@ -528,9 +528,11 @@ def test_required_graph_inputs():
     y = pt.constant(2)
     z = shared(1)
     a = pt.sum(x + y + z)
+    b = pt.true_div(x, y)
 
     res = list(required_graph_inputs([a]))
-    assert res == [x]
+    res1 = list(required_graph_inputs(b))
+    assert res, res1 == [x]
 
 
 def test_variables_and_orphans():