how to check if a word exists in a list code example

Example 1: Check if element in list Python

listA = [item1, item2, item3]
if item4 in listA:
  print('yes, item4 is in the list')
else:
  print('no, item4 is not in the list')

Example 2: how to check an array for a value in python

s = set(a)
if 7 in s:
  # do stuff