use whitespace in order to make the code as readable as possible to humanssince python will ignore it anyway variables and variable types we are used to variables in mathematicssuch as and in the interest formula above we can use variables in program tooand this makes the program easier to read and understandprimary amount primary ( + / )** print(amountthis program spans several lines of text and uses variablesbut otherwise performs the same calculations and produces the exact same output as the one-line program above stillthe use of variables has few advantageseven in this very simple example one is that the program becomes easier to readsince the meaning of the numbers becomes more intuitive and the formula is easier to recognize another advantagewhich could be more importantis that it becomes easier to change the value of one of the variables this advantage becomes even more obvious in more complex formulas where the same variable occurs multiple times having to change the code in multiple places each time new value is needed is guaranteed to introduce errors if the same number occurs more than once in programit should always be stored in variable the instructions in the program above are called statementsand are executed one by one when the program is run it is common to have one statement per linealthough it is possible to put multiple statements on one lineseparated by semicolonsas in primary = for people new to programmingespecially those used to reading mathematicsit is worth noting the strict sequence in which the lines are executed in the mathematical equation abovewe first introduced the formula itselfand then defined and explained the variables used in the formula (prnand aon the next line this approach is completely standard in mathematicsbut it makes no sense in programming programs are executed line by line from the topso so all the variables must be defined above the line where they are used the choice of variable names is up to the programmer andgenerallythere is great flexibility in choosing such names in mathematicsit is common to use single letter for variablebut variable in python program can be any word containing the letters -za-zunderscore and the digits - but it cannot start with digit variable names in python are also case-sensitive