bob {'job''dev''name''bob''age' zipping notice how the left-to-right order of dictionary keys is scrambled mappings are not positionally orderedso unless you're luckythey'll come back in different order than you typed them the exact order may vary per pythonbut you shouldn' depend on itand shouldn' expect yours to match that in this book nesting revisited in the prior examplewe used dictionary to describe hypothetical personwith three keys supposethoughthat the information is more complex perhaps we need to record first name and last namealong with multiple job titles this leads to another application of python' object nesting in action the following dictionarycoded all at once as literalcaptures more structured informationrec {'name'{'first''bob''last''smith'}'jobs'['dev''mgr']'age' herewe again have three-key dictionary at the top (keys "name,"jobs,and "age")but the values have become more complexa nested dictionary for the name to support multiple partsand nested list for the jobs to support multiple roles and future expansion we can access the components of this structure much as we did for our listbased matrix earlierbut this time most indexes are dictionary keysnot list offsetsrec['name'{'last''smith''first''bob''nameis nested dictionary rec['name']['last''smithindex the nested dictionary rec['jobs'['dev''mgr'rec['jobs'][- 'mgr'jobsis nested list index the nested list rec['jobs'append('janitor'expand bob' job description in place rec {'age' 'jobs'['dev''mgr''janitor']'name'{'last''smith''first''bob'}notice how the last operation here expands the nested jobs list--because the jobs list is separate piece of memory from the dictionary that contains itit can grow and shrink freely (object memory layout will be discussed further later in this bookthe real reason for showing you this example is to demonstrate the flexibility of python' core data types as you can seenesting allows us to build up complex information structures directly and easily building similar structure in low-level language like would be tedious and require much more codewe would have to lay out and dictionaries