vfdev-5: @anmolsjoshi or @jasonkriss please merge if OK
diff --git a/ignite/engine/engine.py b/ignite/engine/engine.py
index e6f9620a..07fbf8c5 100644
--- a/ignite/engine/engine.py
+++ b/ignite/engine/engine.py
@@ -163,6 +163,23 @@ class Engine(object):
                     return True
         return False
 
+    def remove_event_handler(self, handler, event_name):
+        """Remove event handler `handler` from registered handlers of the engine
+
+        Args:
+            handler (callable): the callable event handler that should be removed
+            event_name: The event the handler attached to.
+
+        """
+        if event_name not in self._event_handlers:
+            raise ValueError("Input event name '{}' does not exist".format(event_name))
+
+        new_event_handlers = [(h, args, kwargs) for h, args, kwargs in self._event_handlers[event_name]
+                              if h != handler]
+        if len(new_event_handlers) == len(self._event_handlers[event_name]):
+            raise ValueError("Input handler '{}' is not found among registered event handlers".format(handler))
+        self._event_handlers[event_name] = new_event_handlers
+
     def _check_signature(self, fn, fn_description, *args, **kwargs):
         exception_msg = None
 

Remove handler feature in Engine
I recently encountered the cases where I would like to remove a handler and optionally replace it with another one. The following code is used:
```python
def remove_handler(engine, handler, event_name):
    assert event_name in engine._event_handlers    
    engine._event_handlers[event_name] = [(h, args, kwargs) 
                                          for h, args, kwargs in engine._event_handlers[event_name] 
                                            if h != handler]
```

@alykhantejani @jasonkriss what do you guys think about inserting such method into `Engine` ?
cc @anmolsjoshi 
diff --git a/tests/ignite/engine/test_engine.py b/tests/ignite/engine/test_engine.py
index a3f1d64c..3b9f19fa 100644
--- a/tests/ignite/engine/test_engine.py
+++ b/tests/ignite/engine/test_engine.py
@@ -150,6 +150,38 @@ def test_has_event_handler():
     assert not engine.has_event_handler(m, Events.EPOCH_STARTED)
 
 
+def test_remove_event_handler():
+    engine = DummyEngine()
+
+    with pytest.raises(ValueError, match=r'Input event name'):
+        engine.remove_event_handler(lambda x: x, "an event")
+
+    def on_started(engine):
+        return 0
+
+    engine.add_event_handler(Events.STARTED, on_started)
+
+    with pytest.raises(ValueError, match=r'Input handler'):
+        engine.remove_event_handler(lambda x: x, Events.STARTED)
+
+    h1 = MagicMock()
+    h2 = MagicMock()
+    handlers = [h1, h2]
+    m = MagicMock()
+    for handler in handlers:
+        engine.add_event_handler(Events.EPOCH_STARTED, handler)
+    engine.add_event_handler(Events.EPOCH_COMPLETED, m)
+
+    assert len(engine._event_handlers[Events.EPOCH_STARTED]) == 2
+    engine.remove_event_handler(h1, Events.EPOCH_STARTED)
+    assert len(engine._event_handlers[Events.EPOCH_STARTED]) == 1
+    assert engine._event_handlers[Events.EPOCH_STARTED][0][0] == h2
+
+    assert len(engine._event_handlers[Events.EPOCH_COMPLETED]) == 1
+    engine.remove_event_handler(m, Events.EPOCH_COMPLETED)
+    assert len(engine._event_handlers[Events.EPOCH_COMPLETED]) == 0
+
+
 def test_args_and_kwargs_are_passed_to_event():
     engine = DummyEngine()
     kwargs = {'a': 'a', 'b': 'b'}

pip install -e .
parse_log_pytest
pytest
numpy mock pytest codecov pytest-cov tqdm scikit-learn visdom torchvision tensorboardX gym
apt-get update apt-get install -y gcc
3.6
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs @ file:///opt/conda/conda-bld/attrs_1642510447205/work
certifi==2021.5.30
charset-normalizer==2.0.12
cloudpickle==2.2.1
codecov==2.1.13
coverage==6.2
dataclasses==0.8
decorator==4.4.2
gym==0.26.2
gym-notices==0.0.8
idna==3.10
importlib-metadata @ file:///tmp/build/80754af9/importlib-metadata_1631916693255/work
importlib-resources==5.4.0
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
joblib==1.1.1
jsonpatch==1.32
jsonpointer==2.3
mock==5.2.0
more-itertools @ file:///tmp/build/80754af9/more-itertools_1637733554872/work
networkx==2.5.1
numpy==1.19.5
packaging @ file:///tmp/build/80754af9/packaging_1637314298585/work
Pillow==8.4.0
pluggy @ file:///tmp/build/80754af9/pluggy_1615976315926/work
protobuf==4.21.0
py @ file:///opt/conda/conda-bld/py_1644396412707/work
pyparsing @ file:///tmp/build/80754af9/pyparsing_1635766073266/work
pytest==6.2.4
pytest-cov==4.0.0
-e git+https://github.com/pytorch/ignite.git@62862eaa376bf2a2f854894623921a86ba3ba947#egg=pytorch_ignite
requests==2.27.1
scikit-learn==0.24.2
scipy==1.5.4
six==1.17.0
tensorboardX==2.6.2.2
threadpoolctl==3.1.0
toml @ file:///tmp/build/80754af9/toml_1616166611790/work
tomli==1.2.3
torch==1.10.1
torchvision==0.11.2
tornado==6.1
tqdm==4.64.1
typing_extensions @ file:///opt/conda/conda-bld/typing_extensions_1647553014482/work
urllib3==1.26.20
visdom==0.2.4
websocket-client==1.3.1
zipp @ file:///tmp/build/80754af9/zipp_1633618647012/work

name: ignite
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - attrs=21.4.0=pyhd3eb1b0_0
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - importlib-metadata=4.8.1=py36h06a4308_0
  - importlib_metadata=4.8.1=hd3eb1b0_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - more-itertools=8.12.0=pyhd3eb1b0_0
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - packaging=21.3=pyhd3eb1b0_0
  - pip=21.2.2=py36h06a4308_0
  - pluggy=0.13.1=py36h06a4308_0
  - py=1.11.0=pyhd3eb1b0_0
  - pyparsing=3.0.4=pyhd3eb1b0_0
  - pytest=6.2.4=py36h06a4308_2
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - toml=0.10.2=pyhd3eb1b0_0
  - typing_extensions=4.1.1=pyh06a4308_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zipp=3.6.0=pyhd3eb1b0_0
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - charset-normalizer==2.0.12
      - cloudpickle==2.2.1
      - codecov==2.1.13
      - coverage==6.2
      - dataclasses==0.8
      - decorator==4.4.2
      - gym==0.26.2
      - gym-notices==0.0.8
      - idna==3.10
      - importlib-resources==5.4.0
      - joblib==1.1.1
      - jsonpatch==1.32
      - jsonpointer==2.3
      - mock==5.2.0
      - networkx==2.5.1
      - numpy==1.19.5
      - pillow==8.4.0
      - protobuf==4.21.0
      - pytest-cov==4.0.0
      - requests==2.27.1
      - scikit-learn==0.24.2
      - scipy==1.5.4
      - six==1.17.0
      - tensorboardx==2.6.2.2
      - threadpoolctl==3.1.0
      - tomli==1.2.3
      - torch==1.10.1
      - torchvision==0.11.2
      - tornado==6.1
      - tqdm==4.64.1
      - urllib3==1.26.20
      - visdom==0.2.4
      - websocket-client==1.3.1
prefix: /opt/conda/envs/ignite

tests/ignite/engine/test_engine.py::test_remove_event_handler
tests/ignite/engine/test_engine.py::test_create_supervised_trainer_traced_with_cpu tests/ignite/engine/test_engine.py::test_create_supervised_evaluator_traced_on_cpu
tests/ignite/engine/test_engine.py::test_terminate tests/ignite/engine/test_engine.py::test_invalid_process_raises_with_invalid_signature tests/ignite/engine/test_engine.py::test_add_event_handler_raises_with_invalid_event tests/ignite/engine/test_engine.py::test_add_event_handler_raises_with_invalid_signature tests/ignite/engine/test_engine.py::test_add_event_handler tests/ignite/engine/test_engine.py::test_adding_multiple_event_handlers tests/ignite/engine/test_engine.py::test_has_event_handler tests/ignite/engine/test_engine.py::test_args_and_kwargs_are_passed_to_event tests/ignite/engine/test_engine.py::test_custom_events tests/ignite/engine/test_engine.py::test_on_decorator_raises_with_invalid_event tests/ignite/engine/test_engine.py::test_on_decorator tests/ignite/engine/test_engine.py::test_returns_state tests/ignite/engine/test_engine.py::test_state_attributes tests/ignite/engine/test_engine.py::test_default_exception_handler tests/ignite/engine/test_engine.py::test_custom_exception_handler tests/ignite/engine/test_engine.py::test_current_epoch_counter_increases_every_epoch tests/ignite/engine/test_engine.py::test_current_iteration_counter_increases_every_iteration tests/ignite/engine/test_engine.py::test_stopping_criterion_is_max_epochs tests/ignite/engine/test_engine.py::test_terminate_at_end_of_epoch_stops_run tests/ignite/engine/test_engine.py::test_terminate_at_start_of_epoch_stops_run_after_completing_iteration tests/ignite/engine/test_engine.py::test_terminate_stops_run_mid_epoch tests/ignite/engine/test_engine.py::test_terminate_epoch_stops_mid_epoch tests/ignite/engine/test_engine.py::test_iteration_events_are_fired tests/ignite/engine/test_engine.py::test_create_supervised_trainer tests/ignite/engine/test_engine.py::test_create_supervised_trainer_with_cpu tests/ignite/engine/test_engine.py::test_create_supervised tests/ignite/engine/test_engine.py::test_create_supervised_on_cpu tests/ignite/engine/test_engine.py::test_create_supervised_with_metrics
ignite/engine/engine.py
ignite/engine/engine.py