Simple Names: Global Unless Assigned
Unqualified simple names follow the LEGB lexical scoping rule outlined for functions in Chapter 17:
Assignment (X = value)
Makes names local: creates or changes the name X in the current local scope, unless declared global.
Reference (X)
Looks for the name X in the current local scope, then any and all enclosing functions, then the current global scope, then the built-in scope.
