checking your code online some of the programs in this book are little long although it is very helpful to learn python by typing out the source code for these programsyou may accidentally make typos that cause your programs to crash it may not be obvious where the typo is you can copy and paste the text of your source code to the online diff tool on the book' website the diff tool will show any differences between the source code in the book and the source code you've typed this is an easy way of finding any typos in your program copying and pasting text is very useful computer skillespecially for computer programming there is video tutorial on copying and pasting at this book' website at the online diff tool is at this web pagetutorial on how to use this tool on the book' website more info links on there is lot that you can learn about programming but you don' need to learn all of it now there are several times in this book where you might like to learn these additional details and explanationsbut if included them in this book then it would add many more pages if this largerheavier book accidentally fell on you the weight of these many additional pages would crush youresulting in death insteadi have included --more info|links in this book that you can follow on this book' website you do not have to read this additional information to understand anything in this bookbut it is there if you are curious these (and otherlinks have been shortened and begin with all of the information from these --more info|links can also be downloaded from even though this book is not dangerously heavyplease do not let it fall on you anyway email questions to the authoral@inventwithpython com