an expression is combination of valuesvariablesand operators value all by itself is considered an expressionand so is variableso the following are all legal expressions (assuming that the variable has been assigned value) statement is unit of code that the python interpreter can execute we have seen two kinds of statementprint and assignment technically an expression is also statementbut it is probably simpler to think of them as different things the important difference is that an expression has valuea statement does not interactive mode and script modeone of the benefits of working with an interpreted language is that you can test bits of code in interactive mode before you put them in script but there are differences between interactive mode and script mode that can be confusing for exampleif you are using python as calculatoryou might type miles miles the first line assigns value to milesbut it has no visible effect the second line is an expressionso the interpreter evaluates it and displays the result so we learn that marathon is about kilometers but if you type the same code into script and run ityou get no output at all in script mode an expressionall by itselfhas no visible effect python actually evaluates the expressionbut it doesn' display the value unless you tell it tomiles print (miles this behavior can be confusing at first script usually contains sequence of statements if there is more than one statementthe results appear one at time as the statements execute for example