user input and error handling so farall the values we have assigned to variables have been written directly into our programs if we want different value of variablewe need to edit the code and rerun the program of coursethis is not how we are used to interacting with computer programs usuallya program will receive some input from usersmost often through graphical user interface (guihoweveralthough guis dominate in modern human-computer interactionother ways of interacting with computer programs can be just as efficient andin some casesfar more suitable for processing large amounts of data and automating repetitive tasks in this we will show how we can extend our programs with simple yet powerful systems for user input in particularwe will see how program can receive command line arguments when it is runhow to make program stop and ask for user inputand how program can read data from files side effect of allowing users to interact with programs is that things will often go wrong users will often provide the wrong inputand programs should be able to handle such events without simply stopping and writing cryptic error message to the screen we will introduce concept known as exception handlingwhich is widespread system for handling errors in programsused in python and many other programming languages finallyin this we shall see how to create our own modules that can be imported for use in other programsjust as we have done with the math module in previous reading user input data so farwe have implemented various mathematical formulas that involved input variables and parametersbut all of these values have been hard-coded into the programs to introduce new exampleconsider the following formulawhich gives an estimate of the atmospheric pressure as function of (cthe author( sundnesintroduction to scientific programming with pythonsimula springerbriefs on computing