Python: Essential Reference, Third Edition

Object Equality and Identity

The equality operator (x == y) tests the values of x and y for equality. In the case of lists and tuples, all the elements are compared and evaluated as true if they’re of equal value. For dictionaries, a true value is returned only if x and y have the same set of keys and all the objects with the same key have equal values. Two sets are equal if they have the same elements, which are compared using equality (==).

The identity operators (x is y and x is not y) test two objects to see whether they refer to the same object in memory. In general, it may be the case that x == y, but x is not y.

Comparison between objects of noncompatible types, such as a file and a floating-point number, may be allowed, but the outcome ...