Selecting a Face when adding a sketch

[Hecatron]

Hi,
So using this as a starting point

from build123d import *
from ocp_vscode import *

with BuildPart() as ex1:
    Cylinder(radius=10, height=3)
    with BuildSketch(ex1.faces().sort_by(Axis.Z)[-1]):
        RegularPolygon(radius=7, side_count=6)
        Circle(radius=4, mode=Mode.SUBTRACT)
    extrude(amount=-2, mode=Mode.SUBTRACT)

show(ex1)

I can select the face I want the sketch to be added to by passing it in via the BuildSketch constructor.

But lets say I want to define the sketch before the part

from build123d import *
from ocp_vscode import *

with BuildSketch() as sketch1:
    RegularPolygon(radius=7, side_count=6)
    Circle(radius=4, mode=Mode.SUBTRACT)

with BuildPart() as ex1:
    Cylinder(radius=10, height=3)
    ex1.faces().sort_by(Axis.Z)[-1]
    # How to specify the face to add it to here?
    # ex1.faces().sort_by(Axis.Z)[-1]
    add(sketch1)
    extrude(amount=-2, mode=Mode.SUBTRACT)

show(ex1)

How do I specify which face to add the sketch to without passing it into the BuildSketch constructor?
It just seems to default to the bottom face and the add operator doesn't seem to have a parameter for the face to add it to.

[Hecatron]

Ok I've just discovered this works, although maybe there's a better way

from build123d import *
from ocp_vscode import *

with BuildSketch() as sketch1:
    RegularPolygon(radius=7, side_count=6)
    Circle(radius=4, mode=Mode.SUBTRACT)

with BuildPart() as ex1:
    Cylinder(radius=10, height=3)
    ex1.faces().sort_by(Axis.Z)[-1]
    with BuildSketch(ex1.faces().sort_by(Axis.Z)[-1]) as sketch2:
        add(sketch1)
    extrude(amount=-2, mode=Mode.SUBTRACT)

show(ex1)

[gumyr]

Use Locations, GridLocations, etc. (see https://build123d.readthedocs.io/en/latest/key_concepts.html#locations-context) to position objects within Builders as follows:

with BuildPart() as ex1:
    Cylinder(radius=10, height=3)
    with Locations(ex1.faces().sort_by(Axis.Z)[-1]):
        add(sketch1)
    extrude(amount=-2, mode=Mode.SUBTRACT)

[Hecatron]

right thanks