[Python] If list index exists, do X

I need to code such that if a certain list index exists, then run a function.

My failing code:

n = input ("Define number of actors: ")
count = 0
nams = []
while count < n:
count = count + 1
print "Define name for actor ", count, ":"
nams.append(raw_input())
if nams[2]: # 'if nams[2] exists, do something depending on len(nams)
if len(nams) > 3:
do_something

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