feat(base): add environment() and move isnotebook out of the matplotlib block

isnotebook() lived inside graphics.py's matplotlib try-block, so it vanished
when matplotlib was missing, and it reported False for Google Colab and
JupyterLite. RTB, MVTB and bdsim each grew their own copy as a result.

Add environment(), returning "terminal", "ipython", "jupyter", "colab" or
"jupyterlite", in a new matplotlib-free module, and make isnotebook() a thin
wrapper that is True for jupyter, colab and jupyterlite. smb.isnotebook is
still exported. Tests use a faked get_ipython/sys.modules/sys.platform.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: petercorke

spatialmath/base/__init__.py

@@ -10,6 +10,7 @@
 from spatialmath.base.vectors import *  # lgtm [py/polluting-import]
 from spatialmath.base.symbolic import *  # lgtm [py/polluting-import]
 from spatialmath.base.numeric import *  # lgtm [py/polluting-import]
+from spatialmath.base._environment import *  # lgtm [py/polluting-import]
 
 import importlib
 
@@ -45,7 +46,6 @@
     "plotvol2": "graphics",
     "plotvol3": "graphics",
     "expand_dims": "graphics",
-    "isnotebook": "graphics",
 }
 
 
@@ -392,6 +392,7 @@ def __getattr__(name):
     "plot_cuboid",
     "axes_logic",
     "expand_dims",
+    "environment",
     "isnotebook",
     # spatial.base.numeric
     "numjac",

spatialmath/base/_environment.py

@@ -0,0 +1,78 @@
+# Part of Spatial Math Toolbox for Python
+# Copyright (c) 2000 Peter Corke
+# MIT Licence, see details in top-level file: LICENCE
+
+"""
+Detect the interactive environment that Python is running in.
+
+This module deliberately does not import Matplotlib, so it is cheap to import
+and works when Matplotlib is not installed.
+"""
+
+import sys
+from typing import Literal
+
+__all__ = ["environment", "isnotebook"]
+
+Environment = Literal["terminal", "ipython", "jupyter", "colab", "jupyterlite"]
+
+
+def environment() -> Environment:
+    """
+    Determine the environment that Python is running in
+
+    :return: the environment
+    :rtype: str
+
+    The result is one of:
+
+    ========================  ====================================================
+    ``"terminal"``            standard Python interpreter, or script
+    ``"ipython"``             IPython running in a terminal
+    ``"jupyter"``             Jupyter kernel, eg. JupyterLab, Notebook, VS Code or
+                              qtconsole
+    ``"colab"``               Google Colab
+    ``"jupyterlite"``         JupyterLite, running in the browser (Pyodide)
+    ========================  ====================================================
+
+    .. note:: The different Jupyter front ends (JupyterLab, classic Notebook,
+        VS Code, Jupyter Desktop) cannot be reliably told apart from within the
+        kernel, so all are reported as ``"jupyter"``.  How figures will be
+        rendered depends on the Matplotlib backend, not on the front end.
+
+    :seealso: :func:`isnotebook`
+    """
+    # Colab and JupyterLite both also provide an IPython kernel, so test for
+    # them first
+    if "google.colab" in sys.modules:
+        return "colab"
+    if sys.platform == "emscripten":
+        return "jupyterlite"
+
+    try:
+        shell = get_ipython().__class__.__name__  # type: ignore[name-defined]
+    except NameError:
+        return "terminal"  # probably standard Python interpreter
+
+    if shell == "ZMQInteractiveShell":
+        return "jupyter"  # Jupyter notebook or qtconsole
+    elif shell == "TerminalInteractiveShell":
+        return "ipython"
+    else:
+        return "terminal"  # other type (?)
+
+
+def isnotebook() -> bool:
+    """
+    Determine if code is being run from a Jupyter notebook
+
+    :return: True if running in a Jupyter kernel, Google Colab or JupyterLite
+    :rtype: bool
+
+    :seealso: :func:`environment`
+
+    :references:
+
+        - https://stackoverflow.com/questions/15411967/how-can-i-check-if-code-is-executed-in-the-ipython-notebook/39662359#39662359
+    """
+    return environment() in ("jupyter", "colab", "jupyterlite")

spatialmath/base/graphics.py

@@ -1783,26 +1783,6 @@ def expand_dims(dim: ArrayLike = None, nd: int = 2) -> NDArray:
         else:
             raise ValueError("nd is 2 or 3")
 
-    def isnotebook() -> bool:
-        """
-        Determine if code is being run from a Jupyter notebook
-
-        :references:
-
-            - https://stackoverflow.com/questions/15411967/how-can-i-check-if-code-
-            is-executed-in-the-ipython-notebook/39662359#39662359
-        """
-        try:
-            shell = get_ipython().__class__.__name__
-            if shell == "ZMQInteractiveShell":
-                return True  # Jupyter notebook or qtconsole
-            elif shell == "TerminalInteractiveShell":
-                return False  # Terminal running IPython
-            else:
-                return False  # Other type (?)
-        except NameError:
-            return False  # Probably standard Python interpreter
-
     if __name__ == "__main__":
         import pathlib
 

tests/base/test_environment.py

@@ -0,0 +1,64 @@
+import builtins
+import sys
+
+import pytest
+
+from spatialmath.base import environment, isnotebook
+
+# These tests are mocked: a fake get_ipython() and sys.modules / sys.platform
+# stand in for the real front ends, which cannot be run under CI.
+
+
+def fake_shell(name):
+    shell = type(name, (), {})()
+    return lambda: shell
+
+
+@pytest.fixture
+def plain(monkeypatch):
+    """Standard interpreter: no IPython, not Colab, not Pyodide"""
+    monkeypatch.delattr(builtins, "get_ipython", raising=False)
+    monkeypatch.delitem(sys.modules, "google.colab", raising=False)
+    monkeypatch.setattr(sys, "platform", "linux")
+    return monkeypatch
+
+
+def test_terminal(plain):
+    assert environment() == "terminal"
+    assert not isnotebook()
+
+
+def test_ipython_terminal(plain):
+    plain.setattr(
+        builtins, "get_ipython", fake_shell("TerminalInteractiveShell"), raising=False
+    )
+    assert environment() == "ipython"
+    assert not isnotebook()
+
+
+def test_jupyter(plain):
+    plain.setattr(
+        builtins, "get_ipython", fake_shell("ZMQInteractiveShell"), raising=False
+    )
+    assert environment() == "jupyter"
+    assert isnotebook()
+
+
+def test_unknown_shell(plain):
+    plain.setattr(builtins, "get_ipython", fake_shell("SomethingElse"), raising=False)
+    assert environment() == "terminal"
+    assert not isnotebook()
+
+
+def test_colab(plain):
+    # Colab's shell is not a ZMQInteractiveShell, so detect it by the module
+    plain.setattr(builtins, "get_ipython", fake_shell("Shell"), raising=False)
+    plain.setitem(sys.modules, "google.colab", object())
+    assert environment() == "colab"
+    assert isnotebook()
+
+
+def test_jupyterlite(plain):
+    plain.setattr(sys, "platform", "emscripten")
+    assert environment() == "jupyterlite"
+    assert isnotebook()