Faster startup: ezdxf and vtk imported on use

.coveragerc

@@ -11,3 +11,4 @@ omit =
 exclude_lines =
     # Ignore stub body
     \.\.\.
+    if TYPE_CHECKING:

cadquery/occ_impl/assembly.py

@@ -9,6 +9,7 @@
     Any,
     List,
     cast,
+    TYPE_CHECKING,
 )
 from typing_extensions import Protocol, Self
 from math import degrees, radians
@@ -41,19 +42,15 @@
 from OCP.TopoDS import TopoDS_Shape
 from OCP.gp import gp_EulerSequence
 
-from vtkmodules.vtkRenderingCore import (
-    vtkActor,
-    vtkPolyDataMapper as vtkMapper,
-    vtkRenderer,
-    vtkProp3D,
-)
-
 from .geom import Location
 from .shapes import Shape, Solid, Compound, GlueLiteral, _set_glue, _set_builder_options
 from .exporters.vtk import toString, extractEdgesFaces
 from ..cq import Workplane
 from ..utils import BiDict
 
+if TYPE_CHECKING:
+    from vtkmodules.vtkRenderingCore import vtkRenderer, vtkProp3D
+
 # type definitions
 AssemblyObjects = Union[Shape, Workplane, None]
 
@@ -628,7 +625,9 @@ def toVTKAssy(
     linewidth: float = 2,
     tolerance: float = 1e-3,
     angularTolerance: float = 0.1,
-) -> List[vtkProp3D]:
+) -> "List[vtkProp3D]":
+
+    from vtkmodules.vtkRenderingCore import vtkActor, vtkPolyDataMapper as vtkMapper
 
     rv: List[vtkProp3D] = []
 
@@ -675,7 +674,13 @@ def toVTK(
     color: Tuple[float, float, float, float] = (1.0, 1.0, 1.0, 1.0),
     tolerance: float = 1e-3,
     angularTolerance: float = 0.1,
-) -> vtkRenderer:
+) -> "vtkRenderer":
+
+    from vtkmodules.vtkRenderingCore import (
+        vtkActor,
+        vtkPolyDataMapper as vtkMapper,
+        vtkRenderer,
+    )
 
     renderer = vtkRenderer()
 

cadquery/occ_impl/exporters/assembly.py

@@ -3,12 +3,9 @@
 
 from tempfile import TemporaryDirectory
 from shutil import make_archive
-from typing import Optional
+from typing import Optional, TYPE_CHECKING
 from typing_extensions import Literal
 
-from vtkmodules.vtkIOExport import vtkJSONSceneExporter, vtkVRMLExporter
-from vtkmodules.vtkRenderingCore import vtkRenderWindow
-
 from OCP.XSControl import XSControl_WorkSession
 from OCP.STEPCAFControl import STEPCAFControl_Writer
 from OCP.STEPControl import STEPControl_StepModelType
@@ -52,6 +49,9 @@
 from ..shapes import Shape, Compound
 from ...types import UnitLiterals
 
+if TYPE_CHECKING:
+    from vtkmodules.vtkRenderingCore import vtkRenderWindow
+
 
 class ExportModes:
     DEFAULT = "default"
@@ -392,11 +392,13 @@ def exportCAF(assy: AssemblyProtocol, path: str, binary: bool = False) -> bool:
 
 def _vtkRenderWindow(
     assy: AssemblyProtocol, tolerance: float = 1e-3, angularTolerance: float = 0.1
-) -> vtkRenderWindow:
+) -> "vtkRenderWindow":
     """
     Convert an assembly to a vtkRenderWindow. Used by vtk based exporters.
     """
 
+    from vtkmodules.vtkRenderingCore import vtkRenderWindow
+
     renderer = toVTK(assy, tolerance=tolerance, angularTolerance=angularTolerance)
     renderWindow = vtkRenderWindow()
     renderWindow.AddRenderer(renderer)
@@ -412,6 +414,8 @@ def exportVTKJS(assy: AssemblyProtocol, path: str):
     Export an assembly to a zipped vtkjs. NB: .zip extensions is added to path.
     """
 
+    from vtkmodules.vtkIOExport import vtkJSONSceneExporter
+
     renderWindow = _vtkRenderWindow(assy)
 
     with TemporaryDirectory() as tmpdir:
@@ -433,6 +437,8 @@ def exportVRML(
     Export an assembly to a vrml file using vtk.
     """
 
+    from vtkmodules.vtkIOExport import vtkVRMLExporter
+
     exporter = vtkVRMLExporter()
     exporter.SetFileName(path)
     exporter.SetRenderWindow(_vtkRenderWindow(assy, tolerance, angularTolerance))

cadquery/occ_impl/exporters/dxf.py

@@ -14,9 +14,6 @@
     runtime_checkable,
 )
 
-import ezdxf
-from ezdxf import units, zoom
-from ezdxf.entities import factory
 from OCP.GeomConvert import GeomConvert
 from OCP.gp import gp_Dir
 from OCP.GC import GC_MakeArcOfEllipse
@@ -27,6 +24,8 @@
 from ..geom import Plane, VectorLike
 
 
+_MM = 4  # ezdxf.units.MM, without importing ezdxf at module level
+
 ApproxOptions = Literal["spline", "arc"]
 DxfEntityAttributes = Tuple[
     Literal["ARC", "CIRCLE", "ELLIPSE", "LINE", "SPLINE",], Dict[str, Any]
@@ -85,7 +84,7 @@ def __init__(
         self,
         dxfversion: str = "AC1027",
         setup: Union[bool, List[str]] = False,
-        doc_units: int = units.MM,
+        doc_units: int = _MM,
         *,
         metadata: Union[Dict[str, str], None] = None,
         approx: Optional[ApproxOptions] = None,
@@ -111,6 +110,8 @@ def __init__(
 
         :param tolerance: Approximation tolerance for converting :class:`cadquery.Workplane` objects to DXF entities.
         """
+        import ezdxf
+
         if metadata is None:
             metadata = {}
 
@@ -153,6 +154,8 @@ def add_shape(self, shape: Union[WorkplaneLike, Shape], layer: str = "") -> Self
         :param s: CadQuery Workplane or Shape
         :param layer: layer definition name
         """
+        import ezdxf
+        from ezdxf.entities import factory
 
         if isinstance(shape, WorkplaneLike):
             plane = shape.plane
@@ -372,7 +375,7 @@ def exportDXF(
     approx: Optional[ApproxOptions] = None,
     tolerance: float = 1e-3,
     *,
-    doc_units: int = units.MM,
+    doc_units: int = _MM,
 ) -> None:
     """
     Export Workplane content to DXF. Works with 2D sections.
@@ -385,6 +388,7 @@ def exportDXF(
     :param tolerance: Approximation tolerance.
     :param doc_units: ezdxf document/modelspace :doc:`units <ezdxf-stable:concepts/units>` (in. = ``1``, mm = ``4``).
     """
+    from ezdxf import zoom
 
     dxf = DxfDocument(approx=approx, tolerance=tolerance, doc_units=doc_units)
 
@@ -407,7 +411,7 @@ def exportDXFProjection(
     tolerance: float = 1e-3,
     *,
     up: Optional[VectorLike] = None,
-    doc_units: int = units.MM,
+    doc_units: int = _MM,
 ) -> None:
     """
     Export to DXF using projections. Works with 3D objects.

cadquery/occ_impl/exporters/vtk.py

@@ -1,21 +1,22 @@
-from vtkmodules.vtkIOXML import vtkXMLPolyDataWriter
-from vtkmodules.vtkFiltersCore import vtkAppendPolyData
-from vtkmodules.vtkCommonDataModel import vtkPolyData
-from vtkmodules.vtkFiltersExtraction import vtkExtractCellsByType
-
-from vtkmodules.vtkCommonDataModel import (
-    VTK_TRIANGLE,
-    VTK_LINE,
-    VTK_VERTEX,
-    VTK_POLY_LINE,
-)
+from typing import TYPE_CHECKING
 
 from ..shapes import Shape
 
+if TYPE_CHECKING:
+    from vtkmodules.vtkCommonDataModel import vtkPolyData
 
-def extractEdgesFaces(data: vtkPolyData) -> tuple[vtkPolyData, vtkPolyData]:
+
+def extractEdgesFaces(data: "vtkPolyData") -> "tuple[vtkPolyData, vtkPolyData]":
     """Helper for edges and faces extraction"""
 
+    from vtkmodules.vtkFiltersExtraction import vtkExtractCellsByType
+    from vtkmodules.vtkCommonDataModel import (
+        VTK_TRIANGLE,
+        VTK_LINE,
+        VTK_VERTEX,
+        VTK_POLY_LINE,
+    )
+
     # extract edges
     extr = vtkExtractCellsByType()
     extr.SetInputDataObject(data)
@@ -44,6 +45,8 @@ def exportVTP(
     shape: Shape, fname: str, tolerance: float = 0.1, angularTolerance: float = 0.1
 ):
 
+    from vtkmodules.vtkIOXML import vtkXMLPolyDataWriter
+
     writer = vtkXMLPolyDataWriter()
     writer.SetFileName(fname)
     writer.SetInputData(shape.toVtkPolyData(tolerance, angularTolerance))
@@ -54,6 +57,8 @@ def toString(
     shape: Shape, tolerance: float = 1e-3, angularTolerance: float = 0.1
 ) -> tuple[str, str]:
 
+    from vtkmodules.vtkIOXML import vtkXMLPolyDataWriter
+
     writer_edges = vtkXMLPolyDataWriter()
     writer_edges.SetWriteToOutputString(True)
 

cadquery/occ_impl/importers/dxf.py

@@ -6,8 +6,6 @@
 from ..geom import Vector
 from ..shapes import Shape, Edge, Face, sortWiresByBuildOrder
 
-import ezdxf
-
 from OCP.ShapeAnalysis import ShapeAnalysis_FreeBounds
 from OCP.collections import HSequence_TopoDS_Shape as TopTools_HSequenceOfShape
 from OCP.gp import gp_Pnt
@@ -172,6 +170,7 @@ def _importDXF(
     :param exclude: a list of layer names not to import
     :param include: a list of layer names to import
     """
+    import ezdxf
 
     if exclude and include:
         raise ValueError("you may specify either 'include' or 'exclude' but not both")

cadquery/occ_impl/shapes.py

@@ -11,6 +11,7 @@
     Self,
     TypeAlias,
     TypeVar,
+    TYPE_CHECKING,
     cast as tcast,
     overload,
     Type,
@@ -20,9 +21,6 @@
 
 from warnings import warn
 
-from vtkmodules.vtkCommonDataModel import vtkPolyData
-from vtkmodules.vtkFiltersCore import vtkTriangleFilter, vtkPolyDataNormals
-
 from OCP.ShapeBuild import ShapeBuild_ReShape
 
 from .geom import Vector, VectorLike, BoundBox, Plane, Location, Matrix
@@ -36,6 +34,9 @@
 from ..utils import multimethod, multidispatch, mypyclassmethod
 from ..types import UnitLiterals
 
+if TYPE_CHECKING:
+    from vtkmodules.vtkCommonDataModel import vtkPolyData
+
 # change default OCCT logging level
 from OCP.Message import Message, Message_Gravity
 
@@ -1711,6 +1712,9 @@ def toVtkPolyData(
         Convert shape to vtkPolyData
         """
 
+        # vtk must be loaded before getVtkPolyData(), which returns None otherwise
+        from vtkmodules.vtkFiltersCore import vtkTriangleFilter, vtkPolyDataNormals
+
         vtk_shape = IVtkOCC_Shape(self.wrapped)
         shape_data = IVtkVTK_ShapeData()
         shape_mesher = IVtkOCC_ShapeMesher()

tests/test_lazy_imports.py

@@ -0,0 +1,23 @@
+import os
+import subprocess
+import sys
+
+import cadquery
+
+
+def test_import_does_not_load_ezdxf_or_vtk():
+    # a fresh interpreter: this process has ezdxf and vtk loaded by other tests
+    code = (
+        "import sys, cadquery;"
+        "print({m.split('.')[0] for m in sys.modules} & {'ezdxf', 'vtkmodules'})"
+    )
+    # run next to the package under test; only stdout is checked, since the
+    # interpreter may crash on exit on Windows (#1911)
+    out = subprocess.run(
+        [sys.executable, "-c", code],
+        cwd=os.path.dirname(os.path.dirname(cadquery.__file__)),
+        capture_output=True,
+        text=True,
+    )
+
+    assert out.stdout.strip().endswith("set()"), out.stdout + out.stderr