TopoDS_Shape used to have a .HashCode() method and it now uses the builtin hash() (via .__hash__()).
However it still uses a .IsEqual() method and does not implement == (via .__eq__()).
This leads to counter-intuitive behavior such as:
print(f"{[hash(a)==hash(b) for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
print(f"{[a.IsEqual(b) for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
# but...
print(f"{len(set(edges2) - set(edges1)) = }") # 6 <- would expect 0 as `IsEqual()` and `hash()` suggest the faces are the same
print(f"{[a==b for a,b in zip(edges1,edges2)] = }") # [False, False, False, False, False, False] <- that's why :(if __eq__ was an alias of IsEqual (as can be simulated with TopoDS_Shape.__eq__ = TopoDS_Shape.IsEqual) we'd have
print(f"{[a==b for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
print(f"{len(set(edges2) - set(edges1)) = }") # 0 <- exclude the faces form themselves, nothing left :)Are there any reasons not to do this?
(arguably __bool__ for .IsNull() would be nice too, but that doesn't seem as important as __hash__ and __eq__ being consistent)
full example:
from typing import Iterator
from OCP.BRepPrimAPI import BRepPrimAPI_MakeBox
from OCP.gp import gp_Ax2
from OCP.TopAbs import TopAbs_ShapeEnum
from OCP.TopExp import TopExp_Explorer
from OCP.TopoDS import TopoDS_Shape
def topexp_explorer(
shape: TopoDS_Shape, find: TopAbs_ShapeEnum
) -> Iterator[TopoDS_Shape]:
explorer = TopExp_Explorer(shape, ToFind=find)
while explorer.More():
item = explorer.Current()
yield item
explorer.Next()
box = BRepPrimAPI_MakeBox(gp_Ax2(), 3, 2, 1).Solid()
edges1 = list(topexp_explorer(box, TopAbs_ShapeEnum.TopAbs_FACE))
edges2 = list(topexp_explorer(box, TopAbs_ShapeEnum.TopAbs_FACE))
print(f"{len(edges1) = }") # 6
print(f"{len(edges2) = }") # 6
print(f"{[hash(a)==hash(b) for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
print(f"{[a.IsEqual(b) for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
print(f"{[a==b for a,b in zip(edges1,edges2)] = }") # [False, False, False, False, False, False]
print(f"{len(set(edges2) - set(edges1)) = }") # 6
TopoDS_Shape.__eq__ = TopoDS_Shape.IsEqual
print(f"{[a==b for a,b in zip(edges1,edges2)] = }") # [True, True, True, True, True, True]
print(f"{len(set(edges2) - set(edges1)) = }") # 0
TopoDS_Shapeused to have a.HashCode()method and it now uses the builtinhash()(via.__hash__()).However it still uses a
.IsEqual()method and does not implement==(via.__eq__()).This leads to counter-intuitive behavior such as:
if
__eq__was an alias ofIsEqual(as can be simulated withTopoDS_Shape.__eq__ = TopoDS_Shape.IsEqual) we'd haveAre there any reasons not to do this?
(arguably
__bool__for.IsNull()would be nice too, but that doesn't seem as important as__hash__and__eq__being consistent)full example: