Lazy import tensorboard

src/pytorch_lightning/loggers/tensorboard.py

@@ -19,12 +19,10 @@
 import logging
 import os
 from argparse import Namespace
-from typing import Any, Dict, Mapping, Optional, Union
+from typing import Any, Dict, Mapping, Optional, TYPE_CHECKING, Union
 
 import numpy as np
 from lightning_utilities.core.imports import RequirementCache
-from tensorboardX import SummaryWriter
-from tensorboardX.summary import hparams
 from torch import Tensor
 
 import pytorch_lightning as pl
@@ -40,6 +38,13 @@
 log = logging.getLogger(__name__)
 
 _TENSORBOARD_AVAILABLE = RequirementCache("tensorboard")
+_TENSORBOARDX_AVAILABLE = RequirementCache("tensorboardX")
+if TYPE_CHECKING:
+    # assumes at least one will be installed when type checking
+    if _TENSORBOARD_AVAILABLE:
+        from torch.utils.tensorboard import SummaryWriter
+    else:
+        from tensorboardX import SummaryWriter  # type: ignore[no-redef]
 
 if _OMEGACONF_AVAILABLE:
     from omegaconf import Container, OmegaConf
@@ -109,6 +114,10 @@ def __init__(
         sub_dir: Optional[_PATH] = None,
         **kwargs: Any,
     ):
+        if not _TENSORBOARD_AVAILABLE and not _TENSORBOARDX_AVAILABLE:
+            raise ModuleNotFoundError(
+                "Neither `tensorboard` nor `tensorboardX` is available. Try `pip install`ing either."
+            )
         super().__init__()
         save_dir = os.fspath(save_dir)
         self._save_dir = save_dir
@@ -172,7 +181,7 @@ def sub_dir(self) -> Optional[str]:
 
     @property
     @rank_zero_experiment
-    def experiment(self) -> SummaryWriter:
+    def experiment(self) -> "SummaryWriter":
         r"""
         Actual tensorboard object. To use TensorBoard features in your
         :class:`~pytorch_lightning.core.module.LightningModule` do the following.
@@ -188,6 +197,12 @@ def experiment(self) -> SummaryWriter:
         assert rank_zero_only.rank == 0, "tried to init log dirs in non global_rank=0"
         if self.root_dir:
             self._fs.makedirs(self.root_dir, exist_ok=True)
+
+        if _TENSORBOARD_AVAILABLE:
+            from torch.utils.tensorboard import SummaryWriter
+        else:
+            from tensorboardX import SummaryWriter  # type: ignore[no-redef]
+
         self._experiment = SummaryWriter(log_dir=self.log_dir, **self._kwargs)
         return self._experiment
 
@@ -224,6 +239,12 @@ def log_hyperparams(
 
         if metrics:
             self.log_metrics(metrics, 0)
+
+            if _TENSORBOARD_AVAILABLE:
+                from torch.utils.tensorboard.summary import hparams
+            else:
+                from tensorboardX.summary import hparams  # type: ignore[no-redef]
+
             exp, ssi, sei = hparams(params, metrics)
             writer = self.experiment._get_file_writer()
             writer.add_summary(exp)

tests/tests_pytorch/loggers/test_all.py

@@ -15,22 +15,16 @@
 import inspect
 import pickle
 from unittest import mock
-from unittest.mock import ANY
+from unittest.mock import ANY, Mock
 
 import pytest
 import torch
 
 from pytorch_lightning import Callback, Trainer
 from pytorch_lightning.demos.boring_classes import BoringModel
-from pytorch_lightning.loggers import (
-    CometLogger,
-    CSVLogger,
-    MLFlowLogger,
-    NeptuneLogger,
-    TensorBoardLogger,
-    WandbLogger,
-)
+from pytorch_lightning.loggers import CometLogger, CSVLogger, MLFlowLogger, NeptuneLogger, WandbLogger
 from pytorch_lightning.loggers.logger import DummyExperiment
+from pytorch_lightning.loggers.tensorboard import _TENSORBOARD_AVAILABLE, TensorBoardLogger
 from tests_pytorch.helpers.runif import RunIf
 from tests_pytorch.loggers.test_comet import _patch_comet_atexit
 from tests_pytorch.loggers.test_mlflow import mock_mlflow_run_creation
@@ -300,10 +294,15 @@ def test_logger_with_prefix_all(tmpdir, monkeypatch):
         logger.experiment.__getitem__().log.assert_called_once_with(1.0)
 
     # TensorBoard
-    with mock.patch("pytorch_lightning.loggers.tensorboard.SummaryWriter"):
-        logger = _instantiate_logger(TensorBoardLogger, save_dir=tmpdir, prefix=prefix)
-        logger.log_metrics({"test": 1.0}, step=0)
-        logger.experiment.add_scalar.assert_called_once_with("tmp-test", 1.0, 0)
+    if _TENSORBOARD_AVAILABLE:
+        import torch.utils.tensorboard as tb
+    else:
+        import tensorboardX as tb
+
+    monkeypatch.setattr(tb, "SummaryWriter", Mock())
+    logger = _instantiate_logger(TensorBoardLogger, save_dir=tmpdir, prefix=prefix)
+    logger.log_metrics({"test": 1.0}, step=0)
+    logger.experiment.add_scalar.assert_called_once_with("tmp-test", 1.0, 0)
 
     # WandB
     with mock.patch("pytorch_lightning.loggers.wandb.wandb") as wandb, mock.patch(
@@ -316,17 +315,22 @@ def test_logger_with_prefix_all(tmpdir, monkeypatch):
         logger.experiment.log.assert_called_once_with({"tmp-test": 1.0, "trainer/global_step": 0})
 
 
-def test_logger_default_name(tmpdir):
+def test_logger_default_name(tmpdir, monkeypatch):
     """Test that the default logger name is lightning_logs."""
 
     # CSV
     logger = CSVLogger(save_dir=tmpdir)
     assert logger.name == "lightning_logs"
 
     # TensorBoard
-    with mock.patch("pytorch_lightning.loggers.tensorboard.SummaryWriter"):
-        logger = _instantiate_logger(TensorBoardLogger, save_dir=tmpdir)
-        assert logger.name == "lightning_logs"
+    if _TENSORBOARD_AVAILABLE:
+        import torch.utils.tensorboard as tb
+    else:
+        import tensorboardX as tb
+
+    monkeypatch.setattr(tb, "SummaryWriter", Mock())
+    logger = _instantiate_logger(TensorBoardLogger, save_dir=tmpdir)
+    assert logger.name == "lightning_logs"
 
     # MLflow
     with mock.patch("pytorch_lightning.loggers.mlflow.mlflow"), mock.patch(

tests/tests_pytorch/loggers/test_tensorboard.py

@@ -15,6 +15,7 @@
 import os
 from argparse import Namespace
 from unittest import mock
+from unittest.mock import Mock
 
 import numpy as np
 import pytest
@@ -278,23 +279,28 @@ def training_step(self, *args):
     assert count_steps == model.indexes
 
 
-@mock.patch("pytorch_lightning.loggers.tensorboard.SummaryWriter")
-def test_tensorboard_finalize(summary_writer, tmpdir):
+def test_tensorboard_finalize(monkeypatch, tmpdir):
     """Test that the SummaryWriter closes in finalize."""
+    if _TENSORBOARD_AVAILABLE:
+        import torch.utils.tensorboard as tb
+    else:
+        import tensorboardX as tb
+
+    monkeypatch.setattr(tb, "SummaryWriter", Mock())
     logger = TensorBoardLogger(save_dir=tmpdir)
     assert logger._experiment is None
     logger.finalize("any")
 
     # no log calls, no experiment created -> nothing to flush
-    summary_writer.assert_not_called()
+    logger.experiment.assert_not_called()
 
     logger = TensorBoardLogger(save_dir=tmpdir)
     logger.log_metrics({"flush_me": 11.1})  # trigger creation of an experiment
     logger.finalize("any")
 
     # finalize flushes to experiment directory
-    summary_writer().flush.assert_called()
-    summary_writer().close.assert_called()
+    logger.experiment.flush.assert_called()
+    logger.experiment.close.assert_called()
 
 
 def test_tensorboard_save_hparams_to_yaml_once(tmpdir):

tests/tests_pytorch/test_cli.py

@@ -1330,7 +1330,9 @@ def test_tensorboard_logger_init_args():
         "TensorBoardLogger",
         {
             "save_dir": "tb",  # Resolve from TensorBoardLogger.__init__
-            "comment": "tb",  # Resolve from tensorboard.writer.SummaryWriter.__init__
+        },
+        {
+            "comment": "tb",  # Unsupported resolving from local imports
         },
     )