PERSPECTIVE: We need practice in using files and strings and we don't have much time. Thus this is a short assignment.

PROBLEM BACKGROUND: Assume you're working on a contract where a company is building a mailing list (or, rather, an e-mailing list) by analyzing e-mail messages. Your task is to write a Python program that reads a file (stored in the current working directory) called mail.dat and outputs to a file called addresses.dat, one per line, every e-mail address contained inside the file. (You can see now why this assignment is titled "The Spammer's Delight Problem".) For this assignment, if a whitespace delimited string of characters has an embedded commercial at sign (@) inside it (that is, interior to the string), we shall consider it an e-mail address. However, any trailing commas must be trimmed from addresses. Thus the string "abc@mtsu.edu," must appear in the output file as "abc@mtsu.edu" with the trailing comma removed. Only commas at the end of a string are considered trailing; do not remove non-trailing commas. Do not worry about any other punctuation characters; the only editing your program must do is to remove trailing commas.

IMPLEMENTATION NOTES: Use as your source file name "spammer.py". Don't forget to head your source file with the standard title line and global comments we use for all programming assignments. Be sure to have code to close() both files that you opened.

INPUT/OUTPUT: You should create your own data file(s) to initially test your program. For grading, link the file $PUB/mail.dat into your work area and use it. The command ln s $PUB/mail.dat mail.dat will do that. (Be sure to link not copy the file into your work area.) For your output file, use the filename addresses.dat. Do not write anything to standard output (i.e., do not use any print() function calls in your final product). The first 10 lines of your addresses.dat file should look like: