fix: warn when the given .env path is a directory

CHANGELOG.md

@@ -14,6 +14,7 @@ project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - `set_key` and `unset_key` no longer leave a `.tmp_*` file behind on Windows when writing a read-only `.env` fails, and the error raised is the one from the failed write rather than from cleaning up the temporary file by [@MohammedAlkindi] in [#686]
 - `load_dotenv`, `dotenv_values`, `get_key`, `set_key`, `unset_key` and the CLI `--file` option now expand a leading `~` to the user's home directory by [@veeceey] in [#615]
 - `find_dotenv` and the IPython `%dotenv` magic now expand a leading `~` in the file name by [@theskumar] in [#714]
+- `load_dotenv`, `dotenv_values` and `get_key` now warn when the given `.env` path is a directory instead of silently loading nothing by [@boriskozak] in [#427]
 
 ## [1.2.4] - 2026-10-01
 
@@ -467,6 +468,7 @@ os.PathLike]` instead of just `os.PathLike` (#347 by [@bbc2]).
 [#700]: https://github.com/theskumar/python-dotenv/pull/700
 [#711]: https://github.com/theskumar/python-dotenv/pull/711
 [#714]: https://github.com/theskumar/python-dotenv/pull/714
+[#427]: https://github.com/theskumar/python-dotenv/issues/427
 [790c5c0]: https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311
 
 <!-- contributors -->
@@ -532,6 +534,7 @@ os.PathLike]` instead of just `os.PathLike` (#347 by [@bbc2]).
 [@zueve]: https://github.com/zueve
 [@JYOuyang]: https://github.com/JYOuyang
 [@burnout-projects]: https://github.com/burnout-projects
+[@boriskozak]: https://github.com/boriskozak
 [@cpackham-atlnz]: https://github.com/cpackham-atlnz
 [Unreleased]: https://github.com/theskumar/python-dotenv/compare/v1.2.4...HEAD
 [1.2.4]: https://github.com/theskumar/python-dotenv/compare/v1.2.3...v1.2.4

src/dotenv/main.py

@@ -69,7 +69,13 @@ def _get_stream(self) -> Iterator[IO[str]]:
         elif self.stream is not None:
             yield self.stream
         else:
-            if self.verbose:
+            if self.dotenv_path and os.path.exists(self.dotenv_path):
+                logger.warning(
+                    "python-dotenv could not load configuration file %s: "
+                    "it is not a file.",
+                    self.dotenv_path,
+                )
+            elif self.verbose:
                 logger.info(
                     "python-dotenv could not find configuration file %s.",
                     self.dotenv_path or ".env",

tests/test_main.py

@@ -764,6 +764,53 @@ def test_load_dotenv_no_file_verbose():
     )
 
 
+@pytest.mark.parametrize("verbose", [False, True])
+@mock.patch.dict(os.environ, {}, clear=True)
+def test_load_dotenv_directory_warns(tmp_path, verbose):
+    logger = logging.getLogger("dotenv.main")
+
+    with (
+        mock.patch.object(logger, "warning") as mock_warning,
+        mock.patch.object(logger, "info") as mock_info,
+    ):
+        result = dotenv.load_dotenv(tmp_path, verbose=verbose)
+
+    assert result is False
+    assert os.environ == {}
+    mock_warning.assert_called_once_with(
+        "python-dotenv could not load configuration file %s: it is not a file.",
+        tmp_path,
+    )
+    mock_info.assert_not_called()
+
+
+def test_dotenv_values_directory_warns(tmp_path):
+    logger = logging.getLogger("dotenv.main")
+
+    with mock.patch.object(logger, "warning") as mock_warning:
+        result = dotenv.dotenv_values(tmp_path)
+
+    assert result == {}
+    mock_warning.assert_called_once_with(
+        "python-dotenv could not load configuration file %s: it is not a file.",
+        tmp_path,
+    )
+
+
+@mock.patch.dict(os.environ, {}, clear=True)
+def test_load_dotenv_directory_with_stream_loads(tmp_path):
+    logger = logging.getLogger("dotenv.main")
+
+    with mock.patch.object(logger, "warning") as mock_warning:
+        result = dotenv.load_dotenv(
+            tmp_path, stream=io.StringIO("FOO=bar\n"), verbose=True
+        )
+
+    assert result is True
+    assert os.environ["FOO"] == "bar"
+    mock_warning.assert_not_called()
+
+
 @pytest.mark.skipif(
     sys.platform == "win32", reason="This test assumes case-sensitive variable names"
 )