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The Native Subclassing API

This is the most advanced way to use Python for your gameplay logic, developing plugins or automating tasks.

It resembles the native way you would work with unreal and c++ but in a (more or less ;) pythonic way.

Anything you define in python subclasses of UObjects is automatically exposed to Blueprints. As python is a dynamic language without strong encapsulation concepts, this looks (at least currently) the best approach from a python-developer point of view.

The system is still under heavy development and new ideas are popping up constantly (the main objective is to simplify and speed up end-users development)

NOTE: currently it works only on python3 as it heavily relies on function annotations.

Subclassing

You can define new classes using standard python subclassing:

import unreal_engine as ue
from unreal_engine.classes import Character, PawnSensingComponent, Pawn

class Monster(Character):

    def __init__(self):
        self.sensor = self.add_actor_component(PawnSensingComponent, 'Sensor')
        
    # properties can only be set starting from begin play
    def ReceiveBeginPlay():
        self.sensor.SightRadius = 17000
        
    def OnSeePawn(self, pawn : Pawn):
        ue.print_string('seen {}'.format(pawn))

Another example for a custom trigger:

import unreal_engine as ue
from unreal_engine.classes import TriggerBox, Actor

class ExplodeTrigger(TriggerBox):

    def ReceiveActorBeginOverlap(self, other : Actor):
        ue.log('TRIGGERED BY ' + str(other))

Properties

Properties can be added to your class as static python class properties:

import unreal_engine as ue
from unreal_engine.classes import Character, PawnSensingComponent, Pawn, FloatProperty

class Hero(Character):

    # you can set it from the editor
    UpSpeed = FloatProperty
    
    def ReceiveTick(self, DeltaSeconds: float):
        location = self.get_actor_location()
        location.z += self.UpSpeed * DeltaSeconds
        self.set_actor_location(location)

Array can be specified like this:

import unreal_engine as ue
from unreal_engine.classes import Character, PawnSensingComponent, Pawn, FloatProperty

class Hero(Character):

    # you can set it from the editor as array
    UpSpeed = [FloatProperty]
    
    def ReceiveTick(self, DeltaSeconds: float):
        location = self.get_actor_location()
        location.z += self.UpSpeed[0] * DeltaSeconds
        self.set_actor_location(location)

Functions and Events

Reloading

The hot-reloading system is still under heavy testing, expect a bunch of crashes when you heavily redefine classes.

By the way, the idea is that simply redefining a class in python (for example via unreal_engine.exec) will update the internal unreal definition. Try to stress-test it and report crash backtraces. Thanks a lot !