dictionaries are collections of other objects that are indexed by key instead of by position both dictionaries and lists may be nestedcan grow and shrink on demandand may contain objects of any type moreovertheir space is automatically cleaned up as you go we've also seen that strings and files work hand in hand to support rich variety of binary and text data 've skipped most of the details here in order to provide quick tourso you shouldn' expect all of this to have made sense yet in the next few we'll start to dig deepertaking second pass over python' core object types that will fill in details omitted hereand give you deeper understanding we'll start off the next with an in-depth look at python numbers firstthoughhere is another quiz to review test your knowledgequiz we'll explore the concepts introduced in this in more detail in upcoming so we'll just cover the big ideas here name four of python' core data types why are they called "coredata types what does "immutablemeanand which three of python' core types are considered immutable what does "sequencemeanand which three types fall into that category what does "mappingmeanand which core type is mapping what is "polymorphism,and why should you caretest your knowledgeanswers numbersstringslistsdictionariestuplesfilesand sets are generally considered to be the core object (datatypes typesnoneand booleans are sometimes classified this way as well there are multiple number types (integerfloating pointcomplexfractionand decimaland multiple string types (simple strings and unicode strings in python xand text strings and byte strings in python they are known as "coretypes because they are part of the python language itself and are always availableto create other objectsyou generally must call functions in imported modules most of the core types have specific syntax for generating the objects'spam'for exampleis an expression that makes string and determines the set of operations that can be applied to it because of thiscore types are hardwired into python' syntax in contrastyou must call the built-in open function to create file object (even though this is usually considered core type too an "immutableobject is an object that cannot be changed after it is created numbersstringsand tuples in python fall into this category while you cannot test your knowledgeanswers