Improve morphisms between Drinfeld modules

src/sage/categories/drinfeld_modules.py

@@ -768,3 +768,23 @@ def ore_polring(self):
                 True
             """
             return self.category().ore_polring()
+
+        def ore_variable(self):
+            r"""
+            Return the variable of the Ore polynomial ring of this Drinfeld module.
+
+            EXAMPLES::
+
+                sage: Fq = GF(25)
+                sage: A.<T> = Fq[]
+                sage: K.<z12> = Fq.extension(6)
+                sage: p_root = 2*z12^11 + 2*z12^10 + z12^9 + 3*z12^8 + z12^7 + 2*z12^5 + 2*z12^4 + 3*z12^3 + z12^2 + 2*z12
+                sage: phi = DrinfeldModule(A, [p_root, z12^3, z12^5])
+
+                sage: phi.ore_polring()
+                Ore Polynomial Ring in t over Finite Field in z12 of size 5^12 over its base twisted by Frob^2
+                sage: phi.ore_variable()
+                t
+
+            """
+            return self.category().ore_polring().gen()