turtles_in_turtle_2.py

import turtle
import random
import time

speed = 5
max_interval = 0.3

window = turtle.Screen()
window.tracer(0)
window.bgcolor(0.2, 0.2, 0.2)

dots = []
interval = 0  # initial value only
spawn_time = time.time()
while True:
    # Spawn new dots at random time intervals
    if time.time() - spawn_time > interval:
        interval = random.random() * max_interval
        spawn_time = time.time()
        # Create new turtle
        dot = turtle.Turtle()
        dot.shape("circle")
        dot.color(
            random.random(),
            random.random(),
            random.random(),
        )
        dot.penup()
        dot.left(random.randint(0, 359))
        # Add to list
        dots.append(dot)

    # Move all dots forward and clear those
    # that leave the screen
    for dot in dots:
        dot.forward(speed)
        # Remove dots that leave screen
        if (
            abs(dot.xcor()) > window.window_width() / 2
            or abs(dot.ycor()) > window.window_height() / 2
        ):
            dot.hideturtle()
            # Update needed here to remove image of dot
            # before removing object
            window.update()
            dots.remove(dot)
            turtle.turtles().remove(dot)

    window.title(f"{len(dots) = }  |  {len(turtle.turtles()) = }")
    window.update()