Concepts

Aliasing

• Aliasing refers to objects that have multiple names
• When working with mutable objects (list, dictionary, and class), surprising effects may occur
  • e.g. when passing the names of mutable objects into a function, it may be passed by value or passed by reference

Namespace

Namespace

• A Namespace is a systematic mapping of names to objects
  • most namespace are currently implemented as dictionaries
• Examples of Namespaces:
  • built-in names
  • the global names in a module
  • the local names in a function invocation
  • the set of attributes of an objects
• Names in different namespaces are not related

Attribute

• An Attribute is any name following a dot
• Attributes may be read-only or writable
  • For writable attribute, assignment is possible
  • Writable attributes may also be deleted with the del statement

Namespace Lifetime

Namespace are created and destroyed

• The Namespace for built-in names is created when the Python interpreter starts up, and is never deleted
• The Global Namespace for a module is created when the module definition is read in and normally last until the interpreter quits
• The Local Namespace for a function is created when the function is called, and deleted when the function returns or raises an exception that is not handled within the function

Scope

• A Scope is the text region of code where a namespace can be accessed