[Bug Fix] Allow logger to support indexing (#4595)

* [Bug Fix] Allow logger to support indexing

This should fix #4540

* Adding test for indexes for DummyLogger

* Apply suggestions from code review

Co-authored-by: chaton <thomas@grid.ai>

* pep8

* added test for dummyexperiment

Co-authored-by: chaton <thomas@grid.ai>
Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>
Co-authored-by: Nicki Skafte <skaftenicki@gmail.com>
Co-authored-by: Sean Naren <sean.narenthiran@gmail.com>

pytorch_lightning/loggers/base.py

@@ -409,6 +409,11 @@ class DummyExperiment(object):
     def __getattr__(self, _):
         return self.nop
 
+    def __getitem__(self, idx):
+        # enables self.logger[0].experiment.add_image
+        # and self.logger.experiment[0].add_image(...)
+        return self
+
 
 class DummyLogger(LightningLoggerBase):
     """ Dummy logger for internal use. Is usefull if we want to disable users
@@ -437,6 +442,9 @@ class DummyLogger(LightningLoggerBase):
     def version(self):
         pass
 
+    def __getitem__(self, idx):
+        return self
+
 
 def merge_dicts(
         dicts: Sequence[Mapping],

tests/loggers/test_base.py

@@ -20,6 +20,7 @@ import numpy as np
 
 from pytorch_lightning import Trainer
 from pytorch_lightning.loggers import LightningLoggerBase, LoggerCollection
+from pytorch_lightning.loggers.base import DummyLogger, DummyExperiment
 from pytorch_lightning.utilities import rank_zero_only
 from tests.base import EvalModelTemplate
 
@@ -215,6 +216,16 @@ def test_with_accumulate_grad_batches():
     assert logger.history == {0: {'loss': 0.5623850983416314}, 1: {'loss': 0.4778883735637184}}
 
 
+def test_dummyexperiment_support_indexing():
+    experiment = DummyExperiment()
+    assert experiment[0] == experiment
+
+
+def test_dummylogger_support_indexing():
+    logger = DummyLogger()
+    assert logger[0] == logger
+
+
 def test_np_sanitization():
     class CustomParamsLogger(CustomLogger):
         def __init__(self):