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Script variables

Eight names injected into every item script, describing the item that ran it.

The same reference is available inside the tool: the {} button in the script editor inserts any of them, and the header comment at the top of a new script lists them.

The list

Name What it is
__CONTROLS__ The item's bound controls. Sets are returned as sets, not expanded
__FLATCONTROLS__ The same, with sets expanded to their contents. Usually the one you want
__NAMESPACE__ The picker's current namespace
__SELF__ The PickerItem instance itself — colour, size, position, flags
__UUID__ This item's id, the same string saved as item_uuid
__ITEM__ Item helper — find and change other items
__LAYER__ Layer helper — Am_Picker's own layers, not Maya display layers
__INIT__ True while the picker is being built. Guard side effects with if not __INIT__:

__CONTROLS__ and __FLATCONTROLS__

The difference matters when an item is bound to a Maya set:

# Item bound to "faceControls_set", which contains 40 controls.
__CONTROLS__      # ['kamal:faceControls_set']
__FLATCONTROLS__  # ['kamal:L_brow_ctrl', 'kamal:R_brow_ctrl', ...]

Both arrive with the namespace already applied, so you can pass them straight to cmds without any further work.

Reach for __FLATCONTROLS__ unless you specifically want to operate on the set object itself.

__SELF__ and __ITEM__

__SELF__ is the item running the script. __ITEM__ is a helper for reaching other items, and __ITEM__.current is the same object as __SELF__.

Call Does
__ITEM__.current This item — identical to __SELF__
__ITEM__.by_uuid("a1b2c3d4-…") Find an item by its id
__ITEM__.all_pickers() Every item on the canvas
__ITEM__.set_visible(target, on) Show or hide an item
__ITEM__.is_visible(target) Query it

The returned PickerItem exposes the same things the Channel Box edits — colour, text, scale, selectable, movable, z-depth, position, rotation:

# A button that hides a whole sub-board when clicked.
if not __INIT__:
    board = __ITEM__.by_uuid("a1b2c3d4-5e6f-7890-abcd-ef1234567890")
    __ITEM__.set_visible(board, not __ITEM__.is_visible(board))

# Make this item non-selectable once it has been used.
__ITEM__.current.set_selectable(False)

Getting a UUID

Select the item and press Ctrl+Shift+C — Copy UUIDs — then paste it into your script. Do not type them out.

__LAYER__

Am_Picker's own layers, as seen in the Picker Outliner. Nothing to do with Maya display layers.

Call Does
__LAYER__.current The layer this item is on
__LAYER__.names() Every layer name in the tab
__LAYER__.set_visible(name, on) Show or hide a layer
__LAYER__.is_visible(name) Query it 
# One button that turns the detail controls on and off.
if not __INIT__:
    __LAYER__.set_visible("Tweakers", not __LAYER__.is_visible("Tweakers"))

This is a good pattern: a visible button on the canvas is far more discoverable than the right-click Layers menu, especially for a layer people toggle constantly.

__INIT__

True while the item is being created, false on a real click.

Its purpose is to stop a script from firing at build time. Without it, a script that resets a limb can run while the picker is loading:

if not __INIT__:
    # Only on a click.
    reset_the_limb()

Anything with a side effect belongs inside the guard. Reads and appearance changes generally do not need it.

__NAMESPACE__

The picker's current namespace, including its trailing colon when there is one, and an empty string when there is not — so it concatenates cleanly:

cmds.select(__NAMESPACE__ + "faceControls_set")

Use this rather than hard-coding a namespace. It is what lets the picker follow whichever copy of the rig the animator is working on.

MEL

MEL scripts get the same information. Choose MEL in the editor and the variables are made available in MEL's syntax.

For anything beyond a one-line command, Python is the better choice — the completion, the error messages and the variable helpers are all richer there.