although we're focusing on built-in numbers right nowall python operators may be overloaded ( implementedby python classes and extension types to work on objects you create for instanceyou'll see later that objects coded with classes may be added or concatenated with + expressionsindexed with [iexpressionsand so on furthermorepython itself automatically overloads some operatorssuch that they perform different actions depending on the type of built-in objects being processed for examplethe operator performs addition when applied to numbers but performs concatenation when applied to sequence objects such as strings and lists in factcan mean anything at all when applied to objects you define with classes as we saw in the prior this property is usually called polymorphism-- term indicating that the meaning of an operation depends on the type of the objects being operated on we'll revisit this concept when we explore functions in because it becomes much more obvious feature in that context numbers in action on to the codeprobably the best way to understand numeric objects and expressions is to see them in actionso with those basics in hand let' start up the interactive command line and try some simple but illustrative operations (be sure to see for pointers if you need help starting an interactive sessionvariables and basic expressions first of alllet' exercise some basic math in the following interactionwe first assign two variables ( and bto integers so we can use them later in larger expression variables are simply names--created by you or python--that are used to keep track of information in your program we'll say more about this in the next but in pythonvariables are created when they are first assigned values variables are replaced with their values when used in expressions variables must be assigned before they can be used in expressions variables refer to objects and are never declared ahead of time in other wordsthese assignments cause the variables and to spring into existence automaticallypython name creatednot declared ahead of time 've also used comment here recall that in python codetext after mark and continuing to the end of the line is considered to be comment and is ignored by numbers in action