ResourceStack

ResourceStack represents a collection of resources stacked together into a single resource. It can grow along the x, y or z axis. This is useful when you want to treat multiple resources as a single unit, for instance stacking lids vertically or arranging plates side by side before placing them on the deck.

Because the stack is itself a Resource, it can be assigned to other resources or the deck like any other labware. When the stack grows along the z-axis it behaves like a traditional stack where items are added and removed from the top.

Below we demonstrate creating stacks in different orientations and interacting with them.

from pylabrobot.resources import Resource, Plate, Lid, Coordinate
from pylabrobot.resources import ResourceStack

Creating an empty stack

Pass the name and direction of growth ("x", "y", or "z").

stack_x = ResourceStack("stack_x", "x")
stack_y = ResourceStack("stack_y", "y")
stack_z = ResourceStack("stack_z", "z")
(stack_x.children, stack_y.children, stack_z.children)

([], [], [])

Stacking resources at construction time

You can also supply a list of resources which will be assigned immediately.

stack = ResourceStack(
    "stack",
    "x",
    [
        Resource("A", size_x=10, size_y=10, size_z=10),
        Resource("B", size_x=10, size_y=10, size_z=10),
    ],
)
([child.name for child in stack.children], stack.get_size_x())

(['A', 'B'], 20)

The total size along the x-axis equals the sum of the children sizes.

stack_y2 = ResourceStack(
    "stack_y2",
    "y",
    [
        Resource("A", size_x=10, size_y=10, size_z=10),
        Resource("B", size_x=10, size_y=10, size_z=10),
    ],
)
stack_y2.get_size_y()

20

Adding and removing items

New items are positioned automatically at the edge returned by get_resource_stack_edge(). When stacking in the z direction you can only remove the current top item.

lid1 = Lid(name="L1", size_x=10, size_y=10, size_z=5, nesting_z_height=1)
lid2 = Lid(name="L2", size_x=10, size_y=10, size_z=5, nesting_z_height=1)
stack_z.assign_child_resource(lid1)
stack_z.assign_child_resource(lid2)
stack_z.get_top_item().name

'L2'

stack_z.unassign_child_resource(lid2)
stack_z.get_top_item().name

'L1'

Attempting to remove lid1 now would raise a ValueError because it is not the top item in this z-growing stack.

Using a ResourceStack as a stacking area

A common use case is stacking plates next to a reader or washer. After placing a plate on the stack you can retrieve it again using get_top_item().

plate = Plate("p1", size_x=1, size_y=1, size_z=1, ordered_items={})
stacking_area = ResourceStack("stacking_area", "z")
stacking_area.assign_child_resource(plate)
stacking_area.get_top_item() is plate

True

When using a :class:~pylabrobot.liquid_handling.liquid_handler.LiquidHandler the stack behaves just like any other resource:

lh.move_plate(stacking_area.get_top_item(), plate_carrier[0])

This allows temporary storage of plates or lids during automated workflows.