how to check if a value is not in an array in python code example

Example 1: python check string not exist in array

arr_test = ["thetung1","thetung2","thetung3"]
title = "thetung"
if title not in arr_test:
	arr_test.append(title)

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

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