pythonthis is all automatic--running the expression creates the entire nested object structure for us in factthis is one of the main benefits of scripting languages like python just as importantlyin lower-level language we would have to be careful to clean up all of the object' space when we no longer need it in pythonwhen we lose the last reference to the object--by assigning its variable to something elsefor example--all of the memory space occupied by that object' structure is automatically cleaned up for usrec now the object' space is reclaimed technically speakingpython has feature known as garbage collection that cleans up unused memory as your program runs and frees you from having to manage such details in your code in standard python ( cpython)the space is reclaimed immediatelyas soon as the last reference to an object is removed we'll study how this works later in for nowit' enough to know that you can use objects freelywithout worrying about creating their space or cleaning up as you go also watch for record structure similar to the one we just coded in and where we'll use it to compare and contrast listsdictionariestuplesnamed tuplesand classes--an array of data structure options with tradeoffs we'll cover in full later missing keysif tests as mappingsdictionaries support accessing items by key onlywith the sorts of operations we've just seen in additionthoughthey also support type-specific operations with method calls that are useful in variety of common use cases for examplealthough we can assign to new key to expand dictionaryfetching nonexistent key is still mistaked {' ' ' ' ' ' two application notes here firstas previewthe rec record we just created really could be an actual database recordwhen we employ python' object persistence system--an easy way to store native python objects in simple files or access-by-key databaseswhich translates objects to and from serial byte streams automatically we won' go into details herebut watch for coverage of python' pickle and shelve persistence modules in and where we'll explore them in the context of filesan oop use caseclassesand changesrespectively secondif you are familiar with json (javascript object notation)--an emerging data-interchange format used for databases and network transfers--this example may also look curiously similarthough python' support for variablesarbitrary expressionsand changes can make its data structures more general python' json library module supports creating and parsing json textbut the translation to python objects is often trivial watch for json example that uses this record in when we study files for larger use casesee mongodbwhich stores data using language-neutral binary-encoded serialization of json-like documentsand its pymongo interface introducing python object types