Membership operators in Python.
(in) and (not in) Use to check the presence of element in the python sequence (eg. string, list, tuple, set and dictionary)
x = 'Hello world'
y = {1:'a',2:'b'}
# Output: True
print('H' in x)
# Output: True
print('hello' not in x)
# Output: True
print(1 in y)
# Output: False
print('a' in y)