Adding and removing entities

Adding and removing individual entities is done via the add_entity and remove_entity methods of World. Revisiting our earlier example of a world with Position and Velocity, this reads as follows:

# Add an entity and get its representation
entity = world.add_entity()

# Remove the entity
world.remove_entity(entity)

Components can be added to the entities directly upon creation. For example, to create an entity with a position at (0, 0) and a velocity of (1, 0), we can do the following:

entity = world.add_entity(Position(0, 0), Velocity(1, 0))

Batch addition

If we want to create multiple entities at once, we can do this in a similar manner via add_entities:

# Add a batch of 10 entities with given position and velocity
_ = world.add_entities(Position(0, 0), Velocity(1, 0), count=10)

In contrast to add_entity, which creates a single entity, add_entities returns an iterator over all newly created entities. Suppose, we want to place the entities all on a line, each one unit apart from the other, we could do this as follows:

# Add a batch of 10 entities with given position and velocity
x_position = 0
for entity in world.add_entities(Position(0, 0), Velocity(1, 0), count=10):
    entity.get[Position]().x = x_position
    x_position += 1

More information on manipulation of and iteration over entities is provided in the upcoming chapters.

Batch removal

If we want to remove multiple entities at once, we need to characterize which entities we mean. To that end, we use queries, which characterize entities by their components. For example, removing all entities that have the component Position can be done with remove_entities as follows:

# Add a batch of 10 entities with given position and velocity
world.remove_entities(world.query[Position]())

More on queries can be found in the chapter Queries and iteration.