IO and Exceptions

Programs are not very useful if they cannot communicate their results. They are also not terribly useful if they cannot change their controlling parameters to compute different results.

We have already been using the print function to display results. This is an example of console input/output. The console is text-based and displays on the screen. It is capable of both input and output. So far we have been allowing the interpreter to arrange the appearance of the output, but we can control that with formatting.

Much of the time our programs will be working with files for both input and output. Files are saved to storage devices such as disk drives or SSDs. Files must be located by the program, made available for reading and/or writing (opened), and eventually closed.

Exceptions occur due to error conditions anywhere in the code. They have wide applicability but are frequently encountered when dealing with input/output and files, so we will look at them in this section.