What are Python namespaces all about?

Namespace is a way to implement scope. In Python, each package, module, class, function and method function owns a "namespace" in which variable names are resolved. When a function,  module or package is evaluated (that is, starts execution), a namespace is created. Think of it as an "evaluation context". When a function, etc., finishes execution, the namespace is dropped. The variables are dropped. Plus there's a global namespace that's used if the name isn't in the local namespace.

Each variable name is checked in the local namespace (the body of the function, the module, etc.), and then checked in the global namespace.

Variables are generally created only in a local namespace. The global and non-local statements can create variables in other than the local namespace.