Repository: Project-MONAI/MONAI

Issue:
Allow feeding Pandas DataFrames directly to CSV datasets
**Is your feature request related to a problem? Please describe.**
In some situations, the user has not access to the csv files but some already generated pandas objects only. 

**Describe the solution you'd like**
In that case, it would be useful to create `CSVDataset` and `CSVIterableDataset` directly from the pandas DataFrames.

**Describe alternatives you've considered**
n/a

**Additional context**
n/a



Discussion:

Resolving patch:
diff --git a/monai/data/dataset.py b/monai/data/dataset.py
--- a/monai/data/dataset.py
+++ b/monai/data/dataset.py
@@ -32,7 +32,7 @@
 
 from monai.data.utils import SUPPORTED_PICKLE_MOD, convert_tables_to_dicts, pickle_hashing
 from monai.transforms import Compose, Randomizable, ThreadUnsafe, Transform, apply_transform
-from monai.utils import MAX_SEED, ensure_tuple, get_seed, look_up_option, min_version, optional_import
+from monai.utils import MAX_SEED, deprecated_arg, get_seed, look_up_option, min_version, optional_import
 from monai.utils.misc import first
 
 if TYPE_CHECKING:
@@ -1222,8 +1222,9 @@ class CSVDataset(Dataset):
         ]
 
     Args:
-        filename: the filename of expected CSV file to load. if providing a list
-            of filenames, it will load all the files and join tables.
+        src: if provided the filename of CSV file, it can be a str, URL, path object or file-like object to load.
+            also support to provide pandas `DataFrame` directly, will skip loading from filename.
+            if provided a list of filenames or pandas `DataFrame`, it will join the tables.
         row_indices: indices of the expected rows to load. it should be a list,
             every item can be a int number or a range `[start, end)` for the indices.
             for example: `row_indices=[[0, 100], 200, 201, 202, 300]`. if None,
@@ -1249,11 +1250,15 @@ class CSVDataset(Dataset):
         transform: transform to apply on the loaded items of a dictionary data.
         kwargs: additional arguments for `pandas.merge()` API to join tables.
 
+    .. deprecated:: 0.8.0
+        ``filename`` is deprecated, use ``src`` instead.
+
     """
 
+    @deprecated_arg(name="filename", new_name="src", since="0.8", msg_suffix="please use `src` instead.")
     def __init__(
         self,
-        filename: Union[str, Sequence[str]],
+        src: Optional[Union[str, Sequence[str]]] = None,  # also can be `DataFrame` or sequense of `DataFrame`
         row_indices: Optional[Sequence[Union[int, str]]] = None,
         col_names: Optional[Sequence[str]] = None,
         col_types: Optional[Dict[str, Optional[Dict[str, Any]]]] = None,
@@ -1261,8 +1266,16 @@ def __init__(
         transform: Optional[Callable] = None,
         **kwargs,
     ):
-        files = ensure_tuple(filename)
-        dfs = [pd.read_csv(f) for f in files]
+        srcs = (src,) if not isinstance(src, (tuple, list)) else src
+        dfs: List = []
+        for i in srcs:
+            if isinstance(i, str):
+                dfs.append(pd.read_csv(i))
+            elif isinstance(i, pd.DataFrame):
+                dfs.append(i)
+            else:
+                raise ValueError("`src` must be file path or pandas `DataFrame`.")
+
         data = convert_tables_to_dicts(
             dfs=dfs, row_indices=row_indices, col_names=col_names, col_types=col_types, col_groups=col_groups, **kwargs
         )
diff --git a/monai/data/iterable_dataset.py b/monai/data/iterable_dataset.py
--- a/monai/data/iterable_dataset.py
+++ b/monai/data/iterable_dataset.py
@@ -9,7 +9,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Callable, Dict, Iterable, Optional, Sequence, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, Sequence, Union
 
 import numpy as np
 from torch.utils.data import IterableDataset as _TorchIterableDataset
@@ -18,7 +18,7 @@
 from monai.data.utils import convert_tables_to_dicts
 from monai.transforms import apply_transform
 from monai.transforms.transform import Randomizable
-from monai.utils import ensure_tuple, optional_import
+from monai.utils import deprecated_arg, optional_import
 
 pd, _ = optional_import("pandas")
 
@@ -147,8 +147,9 @@ class CSVIterableDataset(IterableDataset):
         ]
 
     Args:
-        filename: the filename of CSV file to load. it can be a str, URL, path object or file-like object.
-            if providing a list of filenames, it will load all the files and join tables.
+        src: if provided the filename of CSV file, it can be a str, URL, path object or file-like object to load.
+            also support to provide iter for stream input directly, will skip loading from filename.
+            if provided a list of filenames or iters, it will join the tables.
         chunksize: rows of a chunk when loading iterable data from CSV files, default to 1000. more details:
             https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_csv.html.
         buffer_size: size of the buffer to store the loaded chunks, if None, set to `2 x chunksize`.
@@ -177,11 +178,15 @@ class CSVIterableDataset(IterableDataset):
             https://github.com/pytorch/pytorch/blob/v1.10.0/torch/utils/data/distributed.py#L98.
         kwargs: additional arguments for `pandas.merge()` API to join tables.
 
+    .. deprecated:: 0.8.0
+        ``filename`` is deprecated, use ``src`` instead.
+
     """
 
+    @deprecated_arg(name="filename", new_name="src", since="0.8", msg_suffix="please use `src` instead.")
     def __init__(
         self,
-        filename: Union[str, Sequence[str]],
+        src: Union[Union[str, Sequence[str]], Union[Iterable, Sequence[Iterable]]],
         chunksize: int = 1000,
         buffer_size: Optional[int] = None,
         col_names: Optional[Sequence[str]] = None,
@@ -192,7 +197,7 @@ def __init__(
         seed: int = 0,
         **kwargs,
     ):
-        self.files = ensure_tuple(filename)
+        self.src = src
         self.chunksize = chunksize
         self.buffer_size = 2 * chunksize if buffer_size is None else buffer_size
         self.col_names = col_names
@@ -201,16 +206,46 @@ def __init__(
         self.shuffle = shuffle
         self.seed = seed
         self.kwargs = kwargs
-        self.iters = self.reset()
+        self.iters: List[Iterable] = self.reset()
         super().__init__(data=None, transform=transform)  # type: ignore
 
-    def reset(self, filename: Optional[Union[str, Sequence[str]]] = None):
-        if filename is not None:
-            # update files if necessary
-            self.files = ensure_tuple(filename)
-        self.iters = [pd.read_csv(f, chunksize=self.chunksize) for f in self.files]
+    @deprecated_arg(name="filename", new_name="src", since="0.8", msg_suffix="please use `src` instead.")
+    def reset(self, src: Optional[Union[Union[str, Sequence[str]], Union[Iterable, Sequence[Iterable]]]] = None):
+        """
+        Reset the pandas `TextFileReader` iterable object to read data. For more details, please check:
+        https://pandas.pydata.org/pandas-docs/stable/user_guide/io.html?#iteration.
+
+        Args:
+            src: if not None and provided the filename of CSV file, it can be a str, URL, path object
+                or file-like object to load. also support to provide iter for stream input directly,
+                will skip loading from filename. if provided a list of filenames or iters, it will join the tables.
+                default to `self.src`.
+
+        """
+        src = self.src if src is None else src
+        srcs = (src,) if not isinstance(src, (tuple, list)) else src
+        self.iters = []
+        for i in srcs:
+            if isinstance(i, str):
+                self.iters.append(pd.read_csv(i, chunksize=self.chunksize))
+            elif isinstance(i, Iterable):
+                self.iters.append(i)
+            else:
+                raise ValueError("`src` must be file path or iterable object.")
         return self.iters
 
+    def close(self):
+        """
+        Close the pandas `TextFileReader` iterable objects.
+        If the input src is file path, TextFileReader was created internally, need to close it.
+        If the input src is iterable object, depends on users requirements whether to close it in this function.
+        For more details, please check:
+        https://pandas.pydata.org/pandas-docs/stable/user_guide/io.html?#iteration.
+
+        """
+        for i in self.iters:
+            i.close()
+
     def _flattened(self):
         for chunks in zip(*self.iters):
             yield from convert_tables_to_dicts(
diff --git a/monai/networks/blocks/activation.py b/monai/networks/blocks/activation.py
--- a/monai/networks/blocks/activation.py
+++ b/monai/networks/blocks/activation.py
@@ -19,7 +19,6 @@
     def monai_mish(x, inplace: bool = False):
         return torch.nn.functional.mish(x, inplace=inplace)
 
-
 else:
 
     def monai_mish(x, inplace: bool = False):
@@ -31,7 +30,6 @@ def monai_mish(x, inplace: bool = False):
     def monai_swish(x, inplace: bool = False):
         return torch.nn.functional.silu(x, inplace=inplace)
 
-
 else:
 
     def monai_swish(x, inplace: bool = False):


Test patch:
diff --git a/tests/test_csv_dataset.py b/tests/test_csv_dataset.py
--- a/tests/test_csv_dataset.py
+++ b/tests/test_csv_dataset.py
@@ -14,6 +14,7 @@
 import unittest
 
 import numpy as np
+import pandas as pd
 
 from monai.data import CSVDataset
 from monai.transforms import ToNumpyd
@@ -57,6 +58,7 @@ def prepare_csv_file(data, filepath):
             filepath1 = os.path.join(tempdir, "test_data1.csv")
             filepath2 = os.path.join(tempdir, "test_data2.csv")
             filepath3 = os.path.join(tempdir, "test_data3.csv")
+            filepaths = [filepath1, filepath2, filepath3]
             prepare_csv_file(test_data1, filepath1)
             prepare_csv_file(test_data2, filepath2)
             prepare_csv_file(test_data3, filepath3)
@@ -76,7 +78,7 @@ def prepare_csv_file(data, filepath):
             )
 
             # test multiple CSV files, join tables with kwargs
-            dataset = CSVDataset([filepath1, filepath2, filepath3], on="subject_id")
+            dataset = CSVDataset(filepaths, on="subject_id")
             self.assertDictEqual(
                 {k: round(v, 4) if not isinstance(v, (str, np.bool_)) else v for k, v in dataset[3].items()},
                 {
@@ -102,7 +104,7 @@ def prepare_csv_file(data, filepath):
 
             # test selected rows and columns
             dataset = CSVDataset(
-                filename=[filepath1, filepath2, filepath3],
+                src=filepaths,
                 row_indices=[[0, 2], 3],  # load row: 0, 1, 3
                 col_names=["subject_id", "image", "ehr_1", "ehr_7", "meta_1"],
             )
@@ -120,7 +122,7 @@ def prepare_csv_file(data, filepath):
 
             # test group columns
             dataset = CSVDataset(
-                filename=[filepath1, filepath2, filepath3],
+                src=filepaths,
                 row_indices=[1, 3],  # load row: 1, 3
                 col_names=["subject_id", "image", *[f"ehr_{i}" for i in range(11)], "meta_0", "meta_1", "meta_2"],
                 col_groups={"ehr": [f"ehr_{i}" for i in range(11)], "meta12": ["meta_1", "meta_2"]},
@@ -133,9 +135,7 @@ def prepare_csv_file(data, filepath):
 
             # test transform
             dataset = CSVDataset(
-                filename=[filepath1, filepath2, filepath3],
-                col_groups={"ehr": [f"ehr_{i}" for i in range(5)]},
-                transform=ToNumpyd(keys="ehr"),
+                src=filepaths, col_groups={"ehr": [f"ehr_{i}" for i in range(5)]}, transform=ToNumpyd(keys="ehr")
             )
             self.assertEqual(len(dataset), 5)
             expected = [
@@ -151,7 +151,7 @@ def prepare_csv_file(data, filepath):
 
             # test default values and dtype
             dataset = CSVDataset(
-                filename=[filepath1, filepath2, filepath3],
+                src=filepaths,
                 col_names=["subject_id", "image", "ehr_1", "ehr_9", "meta_1"],
                 col_types={"image": {"type": str, "default": "No image"}, "ehr_1": {"type": int, "default": 0}},
                 how="outer",  # generate NaN values in this merge mode
@@ -161,6 +161,29 @@ def prepare_csv_file(data, filepath):
             self.assertEqual(type(dataset[-1]["ehr_1"]), int)
             np.testing.assert_allclose(dataset[-1]["ehr_9"], 3.3537, rtol=1e-2)
 
+            # test pre-loaded DataFrame
+            df = pd.read_csv(filepath1)
+            dataset = CSVDataset(src=df)
+            self.assertDictEqual(
+                {k: round(v, 4) if not isinstance(v, str) else v for k, v in dataset[2].items()},
+                {
+                    "subject_id": "s000002",
+                    "label": 4,
+                    "image": "./imgs/s000002.png",
+                    "ehr_0": 3.7725,
+                    "ehr_1": 4.2118,
+                    "ehr_2": 4.6353,
+                },
+            )
+
+            # test pre-loaded multiple DataFrames, join tables with kwargs
+            dfs = [pd.read_csv(i) for i in filepaths]
+            dataset = CSVDataset(src=dfs, on="subject_id")
+            self.assertEqual(dataset[3]["subject_id"], "s000003")
+            self.assertEqual(dataset[3]["label"], 1)
+            self.assertEqual(round(dataset[3]["ehr_0"], 4), 3.3333)
+            self.assertEqual(dataset[3]["meta_0"], False)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/test_csv_iterable_dataset.py b/tests/test_csv_iterable_dataset.py
--- a/tests/test_csv_iterable_dataset.py
+++ b/tests/test_csv_iterable_dataset.py
@@ -15,6 +15,7 @@
 import unittest
 
 import numpy as np
+import pandas as pd
 
 from monai.data import CSVIterableDataset, DataLoader
 from monai.transforms import ToNumpyd
@@ -58,6 +59,7 @@ def prepare_csv_file(data, filepath):
             filepath1 = os.path.join(tempdir, "test_data1.csv")
             filepath2 = os.path.join(tempdir, "test_data2.csv")
             filepath3 = os.path.join(tempdir, "test_data3.csv")
+            filepaths = [filepath1, filepath2, filepath3]
             prepare_csv_file(test_data1, filepath1)
             prepare_csv_file(test_data2, filepath2)
             prepare_csv_file(test_data3, filepath3)
@@ -81,18 +83,20 @@ def prepare_csv_file(data, filepath):
                     )
                     break
             self.assertEqual(count, 3)
+            dataset.close()
 
             # test reset iterables
-            dataset.reset(filename=filepath3)
+            dataset.reset(src=filepath3)
             count = 0
             for i, item in enumerate(dataset):
                 count += 1
                 if i == 4:
                     self.assertEqual(item["meta_0"], False)
             self.assertEqual(count, 5)
+            dataset.close()
 
             # test multiple CSV files, join tables with kwargs
-            dataset = CSVIterableDataset([filepath1, filepath2, filepath3], on="subject_id", shuffle=False)
+            dataset = CSVIterableDataset(filepaths, on="subject_id", shuffle=False)
             count = 0
             for item in dataset:
                 count += 1
@@ -120,13 +124,11 @@ def prepare_csv_file(data, filepath):
                         },
                     )
             self.assertEqual(count, 5)
+            dataset.close()
 
             # test selected columns and chunk size
             dataset = CSVIterableDataset(
-                filename=[filepath1, filepath2, filepath3],
-                chunksize=2,
-                col_names=["subject_id", "image", "ehr_1", "ehr_7", "meta_1"],
-                shuffle=False,
+                src=filepaths, chunksize=2, col_names=["subject_id", "image", "ehr_1", "ehr_7", "meta_1"], shuffle=False
             )
             count = 0
             for item in dataset:
@@ -143,10 +145,11 @@ def prepare_csv_file(data, filepath):
                         },
                     )
             self.assertEqual(count, 5)
+            dataset.close()
 
             # test group columns
             dataset = CSVIterableDataset(
-                filename=[filepath1, filepath2, filepath3],
+                src=filepaths,
                 col_names=["subject_id", "image", *[f"ehr_{i}" for i in range(11)], "meta_0", "meta_1", "meta_2"],
                 col_groups={"ehr": [f"ehr_{i}" for i in range(11)], "meta12": ["meta_1", "meta_2"]},
                 shuffle=False,
@@ -161,12 +164,13 @@ def prepare_csv_file(data, filepath):
                     )
                     np.testing.assert_allclose(item["meta12"], [False, True])
             self.assertEqual(count, 5)
+            dataset.close()
 
             # test transform
             dataset = CSVIterableDataset(
                 chunksize=2,
                 buffer_size=4,
-                filename=[filepath1, filepath2, filepath3],
+                src=filepaths,
                 col_groups={"ehr": [f"ehr_{i}" for i in range(5)]},
                 transform=ToNumpyd(keys="ehr"),
                 shuffle=True,
@@ -185,6 +189,7 @@ def prepare_csv_file(data, filepath):
                 self.assertTrue(isinstance(item["ehr"], np.ndarray))
                 np.testing.assert_allclose(np.around(item["ehr"], 4), exp)
             self.assertEqual(count, 5)
+            dataset.close()
 
             # test multiple processes loading
             dataset = CSVIterableDataset(filepath1, transform=ToNumpyd(keys="label"), shuffle=False)
@@ -200,6 +205,45 @@ def prepare_csv_file(data, filepath):
                     np.testing.assert_allclose(item["label"], [4])
                     self.assertListEqual(item["image"], ["./imgs/s000002.png"])
             self.assertEqual(count, 3)
+            dataset.close()
+
+            # test iterable stream
+            iters = pd.read_csv(filepath1, chunksize=1000)
+            dataset = CSVIterableDataset(src=iters, shuffle=False)
+            count = 0
+            for item in dataset:
+                count += 1
+                if count == 3:
+                    self.assertDictEqual(
+                        {k: round(v, 4) if not isinstance(v, str) else v for k, v in item.items()},
+                        {
+                            "subject_id": "s000002",
+                            "label": 4,
+                            "image": "./imgs/s000002.png",
+                            "ehr_0": 3.7725,
+                            "ehr_1": 4.2118,
+                            "ehr_2": 4.6353,
+                        },
+                    )
+                    break
+            self.assertEqual(count, 3)
+            dataset.close()
+
+            # test multiple iterable streams, join tables with kwargs
+            iters = [pd.read_csv(i, chunksize=1000) for i in filepaths]
+            dataset = CSVIterableDataset(src=iters, on="subject_id", shuffle=False)
+            count = 0
+            for item in dataset:
+                count += 1
+                if count == 4:
+                    self.assertEqual(item["subject_id"], "s000003")
+                    self.assertEqual(item["label"], 1)
+                    self.assertEqual(round(item["ehr_0"], 4), 3.3333)
+                    self.assertEqual(item["meta_0"], False)
+            self.assertEqual(count, 5)
+            # manually close the pre-loaded iterables instead of `dataset.close()`
+            for i in iters:
+                i.close()
 
 
 if __name__ == "__main__":