Quite often than not, we might start our project based on a program or programs written by others, such as the programs by our fellow researchers, other students, teachers, programs downloaded from the Internet, or the old programs we wrote ourselves a long time ago. As the first step, we need to know whether our borrowed program contains any errors. These two methods could be used to debug such a program. In a sense, the second method, comment-all-out method, is preferred since it might save us some typing or copy-and-paste time. To debug other programs, the key is to find the locations of the errors. Here is a very useful Python program to get data from Yahoo! Finance: http://goldb.org/ystockquote.html. A beginner could download the program to try small functions contained in the program.