diff --git a/bayes_opt/event.py b/bayes_opt/event.py
index 1cb35c1c2..c1228685a 100644
--- a/bayes_opt/event.py
+++ b/bayes_opt/event.py
@@ -2,12 +2,24 @@
 
 from __future__ import annotations
 
-from enum import Enum
+import sys
+
+if sys.version_info >= (3, 11):
+    from enum import StrEnum
+else:
+    from enum import Enum
+
+    class StrEnum(str, Enum):
+        __slots__ = ()
+
+        def __str__(self) -> str:
+            return str(self.value)
+
 
 __all__ = ["Events", "DEFAULT_EVENTS"]
 
 
-class Events(Enum):
+class Events(StrEnum):
     """Define optimization events.
 
     Behaves similar to enums.
@@ -18,4 +30,4 @@ class Events(Enum):
     OPTIMIZATION_END = "optimization:end"
 
 
-DEFAULT_EVENTS: tuple[Events, ...] = tuple(Events)
+DEFAULT_EVENTS: frozenset[Events] = frozenset(Events)
diff --git a/bayes_opt/logger.py b/bayes_opt/logger.py
index 77e994e0b..f39c73ef0 100644
--- a/bayes_opt/logger.py
+++ b/bayes_opt/logger.py
@@ -211,18 +211,19 @@ def _is_new_max(self, instance):
             self._previous_max = instance.max["target"]
         return instance.max["target"] > self._previous_max
 
-    def update(self, event, instance):
+    def update(self, event: str | Events, instance):
         """Handle incoming events.
 
         Parameters
         ----------
-        event : str
+        event : str or Events
             One of the values associated with `Events.OPTIMIZATION_START`,
             `Events.OPTIMIZATION_STEP` or `Events.OPTIMIZATION_END`.
 
         instance : bayesian_optimization.BayesianOptimization
             The instance associated with the step.
         """
+        event = Events(event)
         if event == Events.OPTIMIZATION_START:
             line = self._header(instance) + "\n"
         elif event == Events.OPTIMIZATION_STEP:
@@ -233,7 +234,7 @@ def update(self, event, instance):
                 colour = self._colour_new_max if is_new_max else self._colour_regular_message
                 line = self._step(instance, colour=colour) + "\n"
         elif event == Events.OPTIMIZATION_END:
-            line = "=" * self._header_length + "\n"
+            line = "=" * (self._header_length or 0) + "\n"
 
         if self._verbose:
             print(line, end="")
@@ -263,13 +264,13 @@ def __init__(self, path, reset=True):
                 self._path.unlink(missing_ok=True)
         super().__init__()
 
-    def update(self, event, instance):
+    def update(self, event: str | Events, instance):
         """
         Handle incoming events.
 
         Parameters
         ----------
-        event : str
+        event : str or Events
             One of the values associated with `Events.OPTIMIZATION_START`,
             `Events.OPTIMIZATION_STEP` or `Events.OPTIMIZATION_END`.
 
@@ -277,6 +278,7 @@ def update(self, event, instance):
             The instance associated with the step.
 
         """
+        event = Events(event)
         if event == Events.OPTIMIZATION_STEP:
             data = dict(instance.res[-1])
 
diff --git a/bayes_opt/observer.py b/bayes_opt/observer.py
index 3571b660b..e6f3f9301 100644
--- a/bayes_opt/observer.py
+++ b/bayes_opt/observer.py
@@ -19,18 +19,19 @@ def __init__(self):
         self._start_time = None
         self._previous_time = None
 
-    def _update_tracker(self, event, instance):
+    def _update_tracker(self, event: str | Events, instance):
         """Update the tracker.
 
         Parameters
         ----------
-        event : str
+        event : str or Events
             One of the values associated with `Events.OPTIMIZATION_START`,
             `Events.OPTIMIZATION_STEP` or `Events.OPTIMIZATION_END`.
 
         instance : bayesian_optimization.BayesianOptimization
             The instance associated with the step.
         """
+        event = Events(event)
         if event == Events.OPTIMIZATION_STEP:
             self._iterations += 1