manually typing it yourself (don' use copy and paste! run the program againand go back and fix any typos or bugs you may have introduced run the program under debuggerso you can carefully execute each line of code one at time to understand what it does find the comments marked with (!to find code that you can modify and then see how this affects the program the next time you run it finallytry to re-create the program yourself from scratch it doesn' have to be an exact copyyou can put your own spin on the program when copying the code from this bookyou don' necessarily have to type the comments (the text at the end of line following the symbol)as these are notes for human programmers and are ignored by python howevertry to write your python code on the same line numbers as the programs in this book to make comparison between the two easier if you have trouble finding typos in your programyou can compare your code to the code in this book with the online diff tool at bigbookpython/diffeach program has been given set of tags to describe itsuch as board gamesimulationartisticand two-player an explanation of each of these tags and cross-index of tags and projects can be found in appendix the projects are listed in alphabetical orderhowever downloading and installing python python is the name of both the programming language and the interpreter software that runs your python code the python software is completely free to download and use you can check if you already have python installed from command line window on windowsopen the command prompt program and then enter py --version if you see output like the followingthen python is installedc:\users\al>py --version python on macos and linuxopen the terminal program and then enter python --version if you see output like the followingthen python is installedpython --version python this book uses python version several backward-incompatible changes were made between python and and the programs in this book require at least python version (released in to run if you see an error message telling you that python cannot be found or the version reports python you can download the latest python installer for your xviii introduction