How to play single player in left 4 dead 2?

I installed the left 4 dead 2 but I can't play single player there is no single player campaign option . so how I can play single player .
Answers:   
Find a pic of Ellis and there u go


Launch by console, make sure you enable it in the options. Press the ~ key to launch the console and type in the command mp_carnival or whatever i can't remember the commands,but you can easily find them on google and sometimes they automaically come up


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