as can will an summary this has discussed techniques for handling collections of related information here is summary of some key ideasa list object is mutable sequence of arbitrary objects items can be accessed by indexing and slicing the items of list can be changed by assignment python lists are similar to arrays in other programming languages python lists are more flexible because their size can vary and they are heterogeneous python lists also support number of useful methods one particularly important data processing operation is sorting python lists have sort method that can be customized by supplying suitable key function this allows programs to sort lists of arbitrary objects classes can use lists to maintain collections stored as instance variables oftentimes using list is more flexible than using separate instance variables for examplea gui application might use list of buttons instead of an instance variable for each button an entire program can be viewed as collection of data and set of operations--an object this is common approach to structuring gui applications python dictionary implements an arbitrary mapping from keys into values it is very useful for representing non-sequential collections exercises review questions true/false the median is the average of set of data standard deviation measures how spread out data set is arrays are usually heterogeneousbut lists are homogeneous python list cannot grow and shrink in size unlike stringspython lists are not mutable