4.9 Membership and identity operators

Membership operators: in/not in

• Determining whether a specific value can be found within a container, such as a list or dictionary
• The in and not in operators, known as membership operators, yield True or False if the left operand matches the value of some element in the right operand, which is always a container.

• Membership operators can be used to check whether a string is a substring, or matching subset of characters, of a larger string.
  • Example, 'abc' in '123abcd' returns True because the substring abc exists in the larger string.

• Finding membership in a dictionary only applies to the key, NOT the value

Example:

Identity operators: is/is not

• The programmer can use the identity operator, is, to check whether two operands are bound to a single object.
• The inverse identity operator, is not, gives the negated value of 'is'. Thus, if x is y is True, then x is not y is False.