computing with formulas false true we see that the evaluation works as expected in one casebut not the otherand this is general problem when comparing floating point numbers in most cases the evaluation worksbut in some cases it does not it is difficult or impossible to predict when it will not workand the behavior of the program thus becomes unpredictable the solution is to always compare floats by using tolerance valueas in tol - print(abs( - tolprint(abs( - toltrue true there is no strict rule for setting the value of the tolerance tolhoweverit should be small enough to be considered insignificant for the application at handbut larger than the typical machine precision - some words are reserved and cannot be used as variables although the choice of variable names is up to the programmersome names are reserved in python and are not allowed to be used these names are andasassertbreakclasscontinuedefdelelifelseexceptexecfinallyforfromglobalifimportinislambdanotorpassprintraisereturntrywithwhileand yield memorizing this list is by no means necessary at this pointand we will use many of these reserved words in our programs laterso it will become quite natural to not use them as variable names howeverfor programming physics and mathematicsit could be worth noting lambdasince the greek letter is common in physics and mathematics formulas since python does not understand greek lettersit is common to just spell them out when programming formulathat isa becomes alphaand so on howeverusing this approach for will lead to an errorand the error message might not be very easy to understand the problem is easily solved by introducing small intentional typo and writing lmbda or similar integer division can cause surprising errors in python and many other programming languagesunintended integer division can sometimes cause surprising results in python this is no longer problemso you are not likely to run into it during this coursebut it is worth being aware ofsince many other programming languages behave in this way recall from above that various operations behave differentlydepending on the type of the variable they work onsuch as in adding two strings versus adding numbers in python the division operator/behaves as in normal division if one of the two arguments is floatbutif both are integers then it will perform integer division and discard the decimal portion of the result consider the following interactive sessionwhich runs python