How Python's Mutable and Immutable Objects Affect Variable Behavior

In Python, every value — including integers, strings, and lists — is an object stored in memory, with each object having a unique identity and type. Objects are either mutable, meaning they can be changed in place (such as lists, dicts, and sets), or immutable, meaning any apparent modification creates an entirely new object (such as integers, strings, and tuples). When two variable names point to the same object, changes made through one name can be visible through the other, a concept known as aliasing. The 'is' operator checks whether two names refer to the identical object in memory, while '==' only compares values, making them behave differently in certain situations. Understanding the difference between in-place mutation and name rebinding — for example, '+=' versus '+' on lists — is essential to avoiding unexpected bugs in Python programs.