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Traffic lights in Python

Archive - Originally posted on "The Horse's Mouth" - 2010-04-13 07:48:20 - Graham Ellis

A really short demo (I'm short on time ... in Dublin and rushing off to do day No. 2 of a Python course!)

A loop - an anonymous list, and a modulo function that lets us cycle round and round the members of that list

for k in range(12):
  light = ["red","red-an-yellow","green","yellow"][k%4]
  print light

Giving me the English traffic lighht colours:

Dorothy-2: grahamellis$ python tlight
red
red-an-yellow
green
yellow
red
red-an-yellow
green
yellow
red
red-an-yellow
green
yellow
Dorothy-2: grahamellis$

Here in Dublin, they miss out the red-an-yellow - straight from red to green!