Use lazy imports in topology to speed up library import.

src/build123d/exporters.py

@@ -30,6 +30,8 @@
 # pylint: disable=no-name-in-module, import-error
 # pylint: disable=too-many-lines
 
+from __future__ import annotations
+from typing import TYPE_CHECKING
 import math
 import xml.etree.ElementTree as ET
 from copy import copy
@@ -41,7 +43,6 @@
 from collections.abc import Callable, Iterable
 
 import ezdxf
-import svgpathtools as PT
 from ezdxf import zoom
 from ezdxf.colors import RGB, aci2rgb
 from ezdxf.math import Vec2
@@ -69,8 +70,10 @@
 )
 from build123d.build_common import UNITS_PER_METER
 
-PathSegment: TypeAlias = PT.Line | PT.Arc | PT.QuadraticBezier | PT.CubicBezier
-"""A type alias for the various path segment types in the svgpathtools library."""
+if TYPE_CHECKING:
+    import svgpathtools as PT  # pylint: disable=C0415
+    PathSegment: TypeAlias = PT.Line | PT.Arc | PT.QuadraticBezier | PT.CubicBezier
+    """A type alias for the various path segment types in the svgpathtools library."""
 
 # ---------------------------------------------------------------------------
 # ---------------------------------------------------------------------------

src/build123d/importers.py

@@ -67,8 +67,6 @@
     XCAFDoc_ColorSurf,
     XCAFDoc_DocumentTool,
 )
-from ocpsvg import ColorAndLabel, import_svg_document
-from svgpathtools import svg2paths
 
 from build123d.build_enums import Align
 from build123d.geometry import Color, Location, Vector, to_align_offset
@@ -270,6 +268,7 @@ def import_svg_as_buildline_code(
     Returns:
         tuple[str, str]: code, builder instance name
     """
+    from svgpathtools import svg2paths  # pylint: disable=C0415
 
     translator = {
         "Line": ["Line", "start", "end"],
@@ -361,6 +360,8 @@ def import_svg(
     Returns:
         ShapeList[Union[Wire, Face]]: objects contained in svg
     """
+    from ocpsvg import ColorAndLabel, import_svg_document  # pylint: disable=C0415
+
     if is_inkscape_label is not None:  # TODO remove for `1.0` release
         msg = "`is_inkscape_label` parameter is deprecated"
         if is_inkscape_label:

src/build123d/objects_curve.py

@@ -30,7 +30,6 @@
 
 import copy as copy_module
 from math import copysign, cos, radians, sin, sqrt
-from scipy.optimize import minimize
 
 from collections.abc import Iterable
 
@@ -204,6 +203,8 @@ def __init__(
         keep: Keep = Keep.TOP,
         mode: Mode = Mode.ADD,
     ):
+        from scipy.optimize import minimize  # pylint: disable=C0415
+
         context: BuildLine | None = BuildLine._get_context(self)
         validate_inputs(context, self)
 

src/build123d/operations_sketch.py

@@ -30,7 +30,6 @@
 from __future__ import annotations
 
 from collections.abc import Iterable
-from scipy.spatial import Voronoi
 from build123d.build_enums import Mode, SortBy
 from build123d.topology import (
     Compound,
@@ -76,6 +75,8 @@ def full_round(
         geometric center of the arc, and the third the radius of the arc
 
     """
+    from scipy.spatial import Voronoi  # pylint: disable=C0415
+
     context: BuildSketch | None = BuildSketch._get_context("full_round")
 
     if not isinstance(edge, Edge):

src/build123d/topology/one_d.py

@@ -60,8 +60,6 @@
 from typing import Literal, overload, TYPE_CHECKING
 from typing_extensions import Self
 from numpy import ndarray
-from scipy.optimize import minimize
-from scipy.spatial import ConvexHull
 
 import OCP.TopAbs as ta
 from OCP.BRep import BRep_Tool
@@ -1972,6 +1970,8 @@ def intersect(
     def param_at_point(self, point: VectorLike) -> float:
         """Normalized parameter at point along Edge"""
 
+        from scipy.optimize import minimize  # pylint: disable=C0415
+
         # Note that this search algorithm would ideally be replaced with
         # an OCP based solution, something like that which is shown below.
         # However, there are known issues with the OCP methods for some
@@ -2438,6 +2438,8 @@ def make_convex_hull(cls, edges: Iterable[Edge], tolerance: float = 1e-3) -> Wir
         Returns:
             Wire: convex hull perimeter
         """
+        from scipy.spatial import ConvexHull  # pylint: disable=C0415
+
         # pylint: disable=too-many-branches, too-many-locals
         # Algorithm:
         # 1) create a cloud of points along all edges

src/build123d/topology/shape_core.py

@@ -60,14 +60,15 @@
     TypeVar,
     Union,
     overload,
+    Literal,
     TYPE_CHECKING,
 )
+from typing_extensions import Self
 
 from collections.abc import Callable, Iterable, Iterator
 
 import OCP.GeomAbs as ga
 import OCP.TopAbs as ta
-from IPython.lib.pretty import pretty, RepresentationPrinter
 from OCP.BOPAlgo import BOPAlgo_GlueEnum
 from OCP.BRep import BRep_Tool
 from OCP.BRepAdaptor import BRepAdaptor_Curve, BRepAdaptor_Surface
@@ -145,10 +146,6 @@
     VectorLike,
     logger,
 )
-from typing_extensions import Self
-
-from typing import Literal
-
 
 if TYPE_CHECKING:  # pragma: no cover
     from .zero_d import Vertex  # pylint: disable=R0801
@@ -157,6 +154,7 @@
     from .three_d import Solid  # pylint: disable=R0801
     from .composite import Compound  # pylint: disable=R0801
     from build123d.build_part import BuildPart  # pylint: disable=R0801
+    from IPython.lib.pretty import RepresentationPrinter
 
 Shapes = Literal["Vertex", "Edge", "Wire", "Face", "Shell", "Solid", "Compound"]
 TrimmingTool = Union[Plane, "Shell", "Face"]
@@ -2266,6 +2264,8 @@ def __repr__(self):
         return repr(ShapeList(self))
 
     def __str__(self):
+        from IPython.lib.pretty import pretty  # pylint: disable=C0415
+
         return pretty(self)
 
     def group(self, key: K):