Lazy load modules

geoviews/__init__.py

@@ -6,18 +6,15 @@
 
 from holoviews import render, save # noqa (API import)
 
-from .annotators import annotate # noqa (API import)
 from .element import ( # noqa (API import)
     _Element, Feature, Tiles, WMTS, LineContours, FilledContours,
     Text, Image, ImageStack, Points, Path, Polygons, Shape, Dataset, RGB,
     Contours, Graph, TriMesh, Nodes, EdgePaths, QuadMesh, VectorField,
     HexTiles, Labels, Rectangles, Segments, WindBarbs
 )
 from .util import load_tiff, from_xarray # noqa (API import)
-from .operation import project                      # noqa (API import)
 from ._warnings import GeoviewsDeprecationWarning, GeoviewsUserWarning  # noqa: F401
 from . import data                                  # noqa (API import)
-from . import operation                             # noqa (API import)
 from . import plotting                              # noqa (API import)
 from . import feature                               # noqa (API import)
 from . import tile_sources                          # noqa (API import)
@@ -42,3 +39,30 @@ def _missing_cmd(*args,**kw): return("install pyct to enable this command (e.g.
     def _err(): raise ValueError(_missing_cmd())
     fetch_data = copy_examples = examples = _err
 del partial, _examples, _copy, _fetch
+
+
+def __getattr__(attr):
+    # Lazy loading heavy modules
+    if attr == 'annotate':
+        from .annotators import annotate
+        return annotate
+    elif attr == 'project':
+        from .operation import project
+        return project
+    elif attr == 'operation':
+        from . import operation
+        return operation
+    raise AttributeError(f"module {__name__} has no attribute {attr!r}")
+
+__all__ = [k for k in locals() if not k.startswith('_')]
+__all__ += ['annotate', 'project', 'operation']
+
+def __dir__():
+    return __all__
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .annotators import annotate
+    from .operation import project
+    from . import operation

geoviews/element/geo.py

@@ -26,13 +26,16 @@
 )
 from shapely.ops import unary_union
 
-try:
-    from iris.cube import Cube
-except (ImportError, OSError):
-    # OSError because environment variable $UDUNITS2_XML_PATH
-    # is sometimes not set. Should be done automatically
-    # when installing the package.
-    Cube = None
+def _get_iris_cube():
+    try:
+        from iris.cube import Cube
+    except (ImportError, OSError):
+        # OSError because environment variable $UDUNITS2_XML_PATH
+        # is sometimes not set. Should be done automatically
+        # when installing the package.
+        Cube = None
+    return Cube
+
 
 try:
     from owslib.wmts import WebMapTileService
@@ -99,7 +102,7 @@ def __init__(self, data, kdims=None, vdims=None, **kwargs):
             crs_data = data.data
         else:
             crs_data = data
-        if Cube and isinstance(crs_data, Cube):
+        if hasattr(crs_data, 'coord_system') and _get_iris_cube() and isinstance(crs_data, _get_iris_cube()):
             coord_sys = crs_data.coord_system()
             if hasattr(coord_sys, 'as_cartopy_projection'):
                 crs = coord_sys.as_cartopy_projection()

geoviews/tests/conftest.py

@@ -0,0 +1,9 @@
+from contextlib import suppress
+
+import geoviews as gv
+
+with suppress(Exception):
+    gv.extension("bokeh")
+
+with suppress(Exception):
+    gv.extension("matplotlib")

geoviews/tests/test_import.py

@@ -0,0 +1,20 @@
+import sys
+from subprocess import check_output
+from textwrap import dedent
+
+
+def test_no_blocklist_imports():
+    check = """\
+    import sys
+    import geoviews as gv
+
+    blocklist = {"panel", "IPython", "datashader", "iris", "dask"}
+    mods = blocklist & set(sys.modules)
+
+    if mods:
+        print(", ".join(mods), end="")
+        """
+
+    output = check_output([sys.executable, '-c', dedent(check)])
+
+    assert output == b""