how does python check if a number is 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: check if a number is in a list python

5 in [3, 4, 5, 6, 7]
# True

9 in [3, 4, 5, 6, 7]
# False