0925. Thinkful - Logic Drills: Traffic light

You're writing code to control your town's traffic lights. You need a function to handle each change from green, to yellow, to red, and then to green again.

Complete the function that takes a string as an argument representing the current state of the light and returns a string representing the state the light should change to.

For example, when the input is green, output should be yellow.

Solution:

from typing import Dict, Optional


CHANGE_LIGHT = {
    "green": "yellow",
    "yellow": "red",
    "red": "green"
}

def update_light(current: str, light: Dict[str, str] = CHANGE_LIGHT, is_on: bool = True) -> Optional[str]:
    if not is_on: return None
    return light[current]