diff --git a/.gitignore b/.gitignore
index 9654eeb..7dd0ffb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,10 +3,7 @@ dist/
 automathon.egg-info/
 workspace.code*
 .eggs/
-automathon/__pycache__/
-automathon/finiteAutomata/__pycache__/
-tests/__pycache__/
-automathon/errors/__pycache__/
+__pycache__/
 build/
 .idea/
 bazel-*
diff --git a/automathon/finite_automata/nfa.py b/automathon/finite_automata/nfa.py
index 5b284eb..74f0e02 100644
--- a/automathon/finite_automata/nfa.py
+++ b/automathon/finite_automata/nfa.py
@@ -377,13 +377,11 @@ def __get_e_closure(
             for st in self.delta[q][""]:
                 if st not in visited:
                     visited.append(st)
-                    ans.extend(
-                        [
-                            k
-                            for k in self.__get_e_closure(st, visited)
-                            if k not in ans
-                        ]
-                    )
+                    ans.extend([
+                        k
+                        for k in self.__get_e_closure(st, visited)
+                        if k not in ans
+                    ])
         return ans
 
     def __ret_get_new_transitions(
@@ -493,9 +491,9 @@ def __extend_local_transitions(
     ) -> None:
         if tmp and s in local_transitions:
             # avoid add repeated values
-            local_transitions[s].extend(
-                [k for k in tmp if k not in local_transitions[s]]
-            )
+            local_transitions[s].extend([
+                k for k in tmp if k not in local_transitions[s]
+            ])
         elif tmp:
             local_transitions[s] = list(tmp)
 
@@ -522,39 +520,33 @@ def minimize(self) -> "NFA":
         local_nfa.renumber()
         return local_nfa
 
-    def renumber(self) -> None:
-        """Change the name of the states, renumbering each of the labels"""
-        idx = 0
-        new_tags = dict()
+    def renumber(self, prefix="q") -> None:
+        """
+        Change the name of the states, renumbering each of the labels
 
-        # New values
-        q = set()
-        delta = dict()
-        f = set()
+        Parameters
+        ----------
+        prefix : str
+            Prefix for the renumbered state names.
+        """
 
-        # Setting the new label for each state
-        tmp_q = list(self.q)
-        tmp_q.sort()
+        delta = dict()
 
-        for _q in tmp_q:
-            new_tags[_q] = str(idx)
-            q.add(str(idx))
-            idx += 1
+        # Create new mappings for states
+        new_tags = {state: f"{prefix}{idx}" for idx, state in enumerate(self.q)}
 
+        # Update states
+        q = {new_tags[state] for state in self.q}
+        f = {new_tags[state] for state in self.f}
         initial_state = new_tags[self.initial_state]
 
-        # Changing the labels for the final states
-        for _f in self.f:
-            f.add(new_tags[_f])
-
+        # Update transitions
         for _q in self.delta:
             delta[new_tags[_q]] = dict()
             for s in self.delta[_q]:
-                nxt_states = list()
-                for nxt_state in self.delta[_q][s]:
-                    nxt_states.append(new_tags[nxt_state])
-
-                delta[new_tags[_q]][s] = set(nxt_states)
+                delta[new_tags[_q]][s] = {
+                    new_tags[nxt_state] for nxt_state in self.delta[_q][s]
+                }
 
         self.q, self.f, self.delta, self.initial_state = (
             q,
diff --git a/tests/test_nfa.py b/tests/test_nfa.py
index e638363..f1e590e 100644
--- a/tests/test_nfa.py
+++ b/tests/test_nfa.py
@@ -178,27 +178,30 @@ def test_intersection(self):
         self.assertFalse(intersection_result.accept("abbbbbb"))
 
     def test_renumber(self):
-        from automathon import DFA
-
-        automata_1 = NFA(
-            q={"3", "1", "2", "0"},
+        q = {"alpha", "beta", "gamma", "sigma"}
+        delta = {
+            "sigma": {"A": {"beta"}},
+            "beta": {"B": {"gamma"}, "": {"gamma"}},
+            "gamma": {"C": {"alpha"}},
+        }
+        initial_state = "sigma"
+        f = {"alpha"}
+
+        automaton = NFA(
+            q=q,
             sigma={"", "A", "B", "C"},
-            delta={
-                "0": {"A": {"1"}},
-                "1": {"B": {"2"}, "": {"2"}},
-                "2": {"C": {"3"}},
-            },
-            initial_state="0",
-            f={"3"},
+            delta=delta,
+            initial_state=initial_state,
+            f=f,
         )
 
-        automata_2: NFA = automata_1.remove_epsilon_transitions()
-        automata_3: DFA = automata_2.get_dfa()
-        automata_4: NFA = automata_3.get_nfa()
-
-        automata_4.renumber()
+        automaton.renumber(prefix="q")
 
-        self.assertTrue(automata_4.is_valid())
+        self.assertTrue(automaton.is_valid())
+        self.assertSetEqual(automaton.q, {"q0", "q1", "q2", "q3"})
+        self.assertNotEqual(automaton.f, f)
+        self.assertNotEqual(automaton.initial_state, initial_state)
+        self.assertNotEqual(automaton.delta, delta)
 
 
 if __name__ == "__main__":