From 7f17531a12ada8e311cfe8cb2774a4387272868b Mon Sep 17 00:00:00 2001
From: Brandon Schabell <brandonschabell@gmail.com>
Date: Fri, 2 Oct 2026 18:32:11 -0500
Subject: [PATCH] Only load the IPython and Jupyter integration modules when
 Dash is imported inside IPython

---
 CHANGELOG.md                      |  1 +
 dash/_jupyter.py                  |  3 +++
 tests/unit/test_jupyter_import.py | 27 +++++++++++++++++++++++++++
 3 files changed, 31 insertions(+)
 create mode 100644 tests/unit/test_jupyter_import.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fb24b979c..85f5996a84 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - [#3646](https://github.com/plotly/dash/pull/3646) Remove React 16 support (`16.14.0` is no longer an accepted value for `REACT_VERSION` / `_set_react_version`).
 
 ### Changed
+- [#4037](https://github.com/plotly/dash/pull/4037) Only load the IPython and Jupyter integration modules when Dash is imported inside IPython. Roughly halves `import dash` time in environments that have IPython installed.
 - [#3987](https://github.com/plotly/dash/pull/3987) Forward FastAPI reload scope options (`reload_dirs`, `reload_excludes`, and `reload_includes`) to Uvicorn when reloading.
 - [#3986](https://github.com/plotly/dash/pull/3986) Adjust `_run_before_hooks` in the `fastapi` backend to honor a response returned by a `before_request` function, matching the `flask` backend's behavior.
 
diff --git a/dash/_jupyter.py b/dash/_jupyter.py
index 85668127df..56ab21f28f 100644
--- a/dash/_jupyter.py
+++ b/dash/_jupyter.py
@@ -15,6 +15,9 @@
 from werkzeug.serving import make_server
 
 try:
+    if "IPython" not in sys.modules:
+        # Not inside IPython: skip the heavy imports, they double the cost of `import dash`.
+        raise ImportError
     from IPython import get_ipython  # type: ignore[attr-defined]
     from IPython.display import IFrame, display, Javascript  # type: ignore[import-not-found]
     from IPython.core.display import HTML  # type: ignore[import-not-found]
diff --git a/tests/unit/test_jupyter_import.py b/tests/unit/test_jupyter_import.py
new file mode 100644
index 0000000000..6a84685de6
--- /dev/null
+++ b/tests/unit/test_jupyter_import.py
@@ -0,0 +1,27 @@
+import subprocess
+import sys
+
+import pytest
+
+pytest.importorskip("IPython")
+
+
+def _run(*args):
+    result = subprocess.run(
+        [sys.executable, *args], capture_output=True, text=True, check=False
+    )
+    assert result.returncode == 0, result.stderr
+
+
+def test_import_dash_does_not_load_ipython():
+    _run("-c", "import dash, sys; assert 'IPython' not in sys.modules")
+
+
+def test_jupyter_support_loads_inside_ipython():
+    _run(
+        "-m",
+        "IPython",
+        "-c",
+        "from dash import _jupyter; "
+        "assert _jupyter._dep_installed and _jupyter.jupyter_dash.in_ipython",
+    )