At the end of most textbooks there is usually an index that lists the pages where a certain word appears. In this problem, you will create an index for a text but, instead of the page number, you will use the line number. Implement the function index() that takes as input the name of a text file and a list of words. For every word in the list, your function will find the lines in the text file where the word occurs and print the corresponding line numbers (where the numbering starts at 1). You should open the file only once.
>>> index('raven. txt', ['raven', 'mortal', 'dying', 'ghost', 'ghastly', 'evil', 'demon'])
raven 44, 53, 55, 64, 78, 97, 104, 111, 118, 120
mortal 30
dying 9
ghost 9
ghastly 82
evil 99,106
demon 122
>>>