How Python Automatically Passes 'self': The Descriptor Protocol Explained

Every Python programmer calls instance methods without manually passing 'self', but few understand why it works. When Python evaluates an attribute like obj.hello, it does not simply retrieve a function — it triggers the descriptor protocol, which transforms the function into a bound method object. This bound method holds a reference to the instance, so when the method is called, the instance is automatically supplied as the first argument. The equivalence of obj.hello() and Demo.hello(obj) reveals this internal mechanism at work. A developer exploring Python internals has documented this process in detail, with experiments and code examples published in a public GitHub repository.