classifying when errors occur errors occur at specific times the two major time frames are compile time runtime no matter when an error occursit causes your application to misbehave the following sections describe each time frame compile time compile time error occurs when you ask python to run the application before python can run the applicationit must interpret the code and put it into form that the computer can understand computer relies on machine code that is specific to that processor and architecture if the instructions you write are malformed or lack needed informationpython can' perform the required conversion it presents an error that you must fix before the application can run fortunatelycompile-time errors are the easiest to spot and fix because the application won' run with compile-time error in placeuser never sees this error category you fix this sort of error as you write your code the appearance of compile-time error should tell you that other typos or omissions could exist in the code it always pays to check the surrounding code to ensure that no other potential problems exist that might not show up as part of the compile cycle runtime runtime error occurs after python compiles the code you write and the computer begins to execute it runtime errors come in several different typesand some are harder to find than others you know you have runtime error when the application suddenly stops running and displays an exception dialog box or when the user complains about erroneous output (or at least instabilitynot all runtime errors produce an exception some runtime errors cause instability (the application freezes)errant outputor data damage runtime errors can affect other applications or create unforeseen damage to the platform on which the application is running in shortruntime errors can cause you quite bit of griefdepending on precisely the kind of error you're dealing with at the time many runtime errors are caused by errant code for exampleyou can misspell the name of variablepreventing python from placing information in the correct variable during execution leaving out an optional but necessary