Sanitize hparams that can't be json-serialized in WandbLogger.log_hyperparameters()

src/lightning/fabric/utilities/logger.py

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
+import json
 from argparse import Namespace
 from dataclasses import asdict, is_dataclass
 from typing import Any, Dict, Mapping, MutableMapping, Optional, Union
@@ -132,6 +132,23 @@ def _sanitize_params(params: Dict[str, Any]) -> Dict[str, Any]:
     return params
 
 
+def _convert_json_serializable(params: Dict[str, Any]) -> Dict[str, Any]:
+    """Convert non-serializable objects in params to string."""
+    return {k: str(v) if not _is_json_serializable(v) else v for k, v in params.items()}
+
+
+def _is_json_serializable(value: Any) -> bool:
+    """Test whether a variable can be encoded as json."""
+    if value is None or isinstance(value, (bool, int, float, str, list, dict)):  # fast path
+        return True
+    try:
+        json.dumps(value)
+        return True
+    except (TypeError, OverflowError):
+        # OverflowError is raised if number is too large to encode
+        return False
+
+
 def _add_prefix(
     metrics: Mapping[str, Union[Tensor, float]], prefix: str, separator: str
 ) -> Mapping[str, Union[Tensor, float]]:

src/lightning/pytorch/CHANGELOG.md

@@ -49,7 +49,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fixed an issue causing a TypeError when using `torch.compile` as a decorator ([#19627](https://github.com/Lightning-AI/pytorch-lightning/pull/19627))
 
--
+
+- Fixed `WandbLogger.log_hyperparameters()` raising an error if hyperparameters are not JSON serializable ([#19769](https://github.com/Lightning-AI/pytorch-lightning/pull/19769))
 
 -
 

src/lightning/pytorch/loggers/wandb.py

@@ -26,7 +26,12 @@
 from torch import Tensor
 from typing_extensions import override
 
-from lightning.fabric.utilities.logger import _add_prefix, _convert_params, _sanitize_callable_params
+from lightning.fabric.utilities.logger import (
+    _add_prefix,
+    _convert_json_serializable,
+    _convert_params,
+    _sanitize_callable_params,
+)
 from lightning.fabric.utilities.types import _PATH
 from lightning.pytorch.callbacks.model_checkpoint import ModelCheckpoint
 from lightning.pytorch.loggers.logger import Logger, rank_zero_experiment
@@ -419,6 +424,7 @@ def watch(
     def log_hyperparams(self, params: Union[Dict[str, Any], Namespace]) -> None:
         params = _convert_params(params)
         params = _sanitize_callable_params(params)
+        params = _convert_json_serializable(params)
         self.experiment.config.update(params, allow_val_change=True)
 
     @override

tests/tests_fabric/utilities/test_logger.py

@@ -11,14 +11,15 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 from argparse import Namespace
 from dataclasses import dataclass
+from pathlib import Path
 
 import numpy as np
 import torch
 from lightning.fabric.utilities.logger import (
     _add_prefix,
+    _convert_json_serializable,
     _convert_params,
     _flatten_dict,
     _sanitize_callable_params,
@@ -167,3 +168,29 @@ def test_add_prefix():
     assert "prefix-metric2" not in metrics
     assert metrics["prefix2_prefix-metric1"] == 1
     assert metrics["prefix2_prefix-metric2"] == 2
+
+
+def test_convert_json_serializable():
+    data = {
+        # JSON-serializable
+        "none": None,
+        "int": 1,
+        "float": 1.1,
+        "bool": True,
+        "dict": {"a": 1},
+        "list": [2, 3, 4],
+        # not JSON-serializable
+        "path": Path("path"),
+        "tensor": torch.tensor(1),
+    }
+    expected = {
+        "none": None,
+        "int": 1,
+        "float": 1.1,
+        "bool": True,
+        "dict": {"a": 1},
+        "list": [2, 3, 4],
+        "path": "path",
+        "tensor": "tensor(1)",
+    }
+    assert _convert_json_serializable(data) == expected

tests/tests_pytorch/loggers/test_wandb.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 import os
 import pickle
+from pathlib import Path
 from unittest import mock
 
 import pytest
@@ -113,9 +114,10 @@ def test_wandb_logger_init(wandb_mock):
     wandb_mock.init().log.assert_called_with({"acc": 1.0, "trainer/global_step": 6})
 
     # log hyper parameters
-    hparams = {"test": None, "nested": {"a": 1}, "b": [2, 3, 4]}
+    hparams = {"none": None, "dict": {"a": 1}, "b": [2, 3, 4], "path": Path("path")}
+    expected = {"none": None, "dict": {"a": 1}, "b": [2, 3, 4], "path": "path"}
     logger.log_hyperparams(hparams)
-    wandb_mock.init().config.update.assert_called_once_with(hparams, allow_val_change=True)
+    wandb_mock.init().config.update.assert_called_once_with(expected, allow_val_change=True)
 
     # watch a model
     logger.watch("model", "log", 10, False)