fill it with none objectsl [none [nonenonenonenonenonenonenonethis doesn' limit the size of the list (it can still grow and shrink later)but simply presets an initial size to allow for future index assignments you could initialize list with zeros the same wayof coursebut best practice dictates using none if the type of the list' contents is variable or not yet known keep in mind that none does not mean "undefined that isnone is somethingnot nothing (despite its name!)--it is real object and real piece of memory that is created and given built-in name by python itself watch for other uses of this special object later in the bookas we'll learn in part ivit is also the default return value of functions that don' exit by running into return statement with result value the bool type while we're on the topic of truthalso keep in mind that the python boolean type boolintroduced in simply augments the notions of true and false in python as we learned in the built-in words true and false are just customized versions of the integers and --it' as if these two words have been preassigned to and everywhere in python because of the way this new type is implementedthis is really just minor extension to the notions of true and false already describeddesigned to make truth values more explicitwhen used explicitly in truth test codethe words true and false are equivalent to and but they make the programmer' intent clearer results of boolean tests run interactively print as the words true and falseinstead of as and to make the type of result clearer you are not required to use only boolean types in logical statements such as ifall objects are still inherently true or falseand all the boolean concepts mentioned in this still work as described if you use other types python also provides bool builtin function that can be used to test the boolean value of an object if you want to make this explicit ( whether it is true--that isnonzero or nonempty)bool( true bool('spam'true bool({}false in practicethoughyou'll rarely notice the boolean type produced by logic testsbecause boolean results are used automatically by if statements and other selection tools we'll explore booleans further when we study logical statements in core types review and summary