[PyGame] Beginner in pygame, I don't know how to use events

[Erepiv1]

Hi everyone,I'm a beginner with pygame. I wanted to use events and look on internet how to use them but the problem is that python keep telling me "NameError: name 'event' is not defined". I don't understand why, all websites I've seen used event like this. Can somebody help me please ?

if event.type == KEYDOWN:
print ("changer de lieu")