Trying a better way of getting length

Signed-off-by: Eric Kerfoot <eric.kerfoot@gmail>

Author: Eric Kerfoot

monai/engines/workflow.py

@@ -13,7 +13,7 @@
 
 import warnings
 from collections.abc import Callable, Iterable, Sequence
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, Sized
 
 import torch
 import torch.distributed as dist
@@ -133,12 +133,9 @@ def __init__(
                 def set_sampler_epoch(engine: Engine) -> None:
                     sampler.set_epoch(engine.state.epoch)
 
-        # if the epoch_length isn't given, attempt to get it from the length of the data loader
-        if epoch_length is None:
-            try:
-                epoch_length = len(data_loader)
-            except TypeError:  # raised when data_loader has an iterable dataset with no length, or is some other type
-                pass  # deliberately leave epoch_length as None
+            # if the epoch_length isn't given, attempt to get it from the length of the data loader
+            if epoch_length is None and isinstance(data_loader.dataset, Sized):
+                epoch_length = len(data_loader.dataset)
 
         # set all sharable data for the workflow based on Ignite engine.state
         self.state: Any = State(