Godot Script Execution Order and Lifecycle

Overview

This post describes the initialization and execution order of scripts that are attached to Nodes in the Godot game engine. I created a GitHub repository that logs these notifications and I recommend playing around with a similar project to familiarize yourself.

Initialization

Member initialization happens in this order:

1. static members are initialized.
2. _static_init() is called.
3. instance members are initialized.
4. _init() is called.
5. @export initialization is applied, which uses property setters if available.

Notifications

Most execution is done from top to bottom of the order of the scene if all nodes are expanded. Exceptions to this are:

• _ready(), NOTIFICATION_READY, and NOTIFICATION_POST_ENTER_TREE are called children first. This means a parent Node will only get these notifications when all its its children have already received these notifications.
• _input() and _unhandled_input() are called bottom to top. This means nodes later in the tree get first chance to handle input.
• _exit_tree() and related notifications are called bottom to top. (Conversely, NOTIFICATION_UNPARENTED are called top to bottom.)

Most notifications are given to all nodes before moving on to the next notification. Exceptions to this are:

• _ready(), NOTIFICATION_READY, and NOTIFICATION_POST_ENTER_TREE happen in that order for each node before moving to the next node.
• _physics_process() and NOTIFICATION_PHYSICS_PROCESS happen in that order for each node before moving to the next node.
• _process() and NOTIFICATION_PROCESS happen in that order for each node before moving to the next node.
• _exit_tree() and related notifications such as NOTIFICATION_EXIT_TREE, Control.NOTIFICATION_MOUSE_EXIT, and CanvasItem.NOTIFICATION_EXIT_CANVAS happen in that order for each node before moving to the next node.

Signals

When a signal is emitted, it is received in the order that the connections were made. Signals are received immediately when they are emitted, even in the middle of a _process sequence, for example.

*_input Methods, Button Methods, etc.

*_input methods are called between _process and _physics_process calls and do not interrupt the sequence of _process or _process_physics. Button signals and methods are similarly called after the all of the *_input methods have been completed.

queue_free()

queue_free() will free those objects without interrupting the _process or _physics_process sequence.