Membership

Just as with strings, Python provides membership operators to ask whether a value occurs in a list. There are two of them, and each returns a Boolean result — True or False.

The in operator

element in list checks whether the element is present in the list. It returns True if it is, and False otherwise:

>>> gases = ['Oxygen', 'Nitrogen', 'Argon']
>>> 'Nitrogen' in gases
True
>>> 'Helium' in gases
False

The not in operator

element not in list is the exact opposite test: it returns True when the element is absent from the list, and False when the element is present:

>>> gases = ['Oxygen', 'Nitrogen', 'Argon']
>>> 'Helium' not in gases
True
>>> 'Nitrogen' not in gases
False

Key points

• in → True if the value is an element of the list, else False.
• not in → True if the value is not an element of the list, else False. …