Object Tree

The Object Tree is an internal representation of all locations and objects present in a Z-machine game, including the player and their inventory.

Each object has parent, child, and sibling object. Parent objects typically contain the child objects. For example if we have a parent object Treasure Chest, it may contain a child object Cutlass that has a sibling object Eye Patch. And the treasure chest may have a parent object Sandy Beach corresponding to the location of the chest. If and when the player reaches the Sandy Beach, the object tree will be rearranged so that the player-object’s sibling will become the Treasure Chest.

Objects additionally have attributes which are set and unset to keep track of the state of an object. For example a window can either be in the open or closed position; this is tracked through its attributes. Finally, the properties of an object are numerical values that determine how the object may be interacted with.

For a great tutorial on the Object Tree, see Z-Machine Standards.

In Jericho, the full object tree can be accessed with jericho.FrotzEnv.get_world_objects(). Jericho also provides shortcuts to particular objects of interest such as the player jericho.FrotzEnv.get_player_object(), the player’s location jericho.FrotzEnv.get_player_location(), and the player’s inventory jericho.FrotzEnv.get_inventory().

ZObject

Jericho’s ZObject is a ctypes structure that providing access to the name, parent, sibling, child, attributes, and properties of an object.

class jericho.ZObject

A Z-Machine Object contains the following fields:

Parameters:
  • num (int) – Object number
  • name (string) – Short object name
  • parent (int) – Object number of parent
  • sibling (int) – Object number of sibling
  • child (int) – Object number of child
  • attr (array) – 32-bit array of object attributes
  • properties (list) – object properties
Example: 
>>> from jericho import *
>>> env = FrotzEnv('zork1.z5')
>>> env.get_player_object()
Obj4: cretin Parent180 Sibling181 Child0 Attributes [7, 9, 14, 30] Properties [18, 17, 7]