Thinkful-Logic Drills: Traffic light - python

Python/8kyu/update_light.py

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+# https://www.codewars.com/kata/58649884a1659ed6cb000072
+# DESCRIPTION:
+# 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.
+
+def update_light(current):
+    dictionary = {
+        "green": "yellow", 
+        "yellow": "red", 
+        "red": "green"
+    } 
+    return dictionary[current]