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Identity operators: is/is not Sometimes a programmer wants to determine whether two variables are the same object. 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. Identity operators do not compare object values; rather, identity operators compare object identities to determine equivalence. Object identity is usually ' the memory address of an object. Thus, identity operators return True only if the operands reference the same object. A common error is to confuse the equivalence operator "==" and the identity operator "is", because a statement such as if x is 3 is valid syntax and is grammatically appealing. Python may confusedly evaluate the statement x is 3 as True, buty is 1000 as False, when x = 3 and y = 1000. Python interpreters typically precreate objects for a small range of numbers to avoid constantly recreating objects for such small values. In the example above, an object for 3 was precreated and thus x references the same object as the literal. However, Python did not precreate an object for 1000. A good practice is to avoid using the identity operators "is" and "is not", unless explicitly testing whether two objects are identical. The id() function can be used to retrieve the identifier of any object. If x is y is True, then id (x) == id (y) is also True. Figure 3.6.4: Identity operators. W = 500 x = 500 + 500 # Create a new object with value 1000 y =w+W Create a second object with value 1000 Z = X # Bind z to the same object as x and x are bound to the same object if z is x: and y are NOT bound to the same object print ('z and x are bound to the same object' ) if z is not y: print ('z and y are NOT bound to the same object' ) Feedback? PARTICIPATION ACTIVITY 3.6.3: Membership and identity operators. Write the simplest expression that captures the desired comparison. 1) x is a key in the dict my_dict Check Show