Exercise 1: Write a simple program to simulate the operation of the
grep command on Unix. Ask the user to enter a regular expression and count the number of lines that matched the regular expression:
$ python grep.py Enter a regular expression: ^Author mbox.txt had 1798 lines that matched ^Author $ python grep.py Enter a regular expression: ^X- mbox.txt had 14368 lines that matched ^X- $ python grep.py Enter a regular expression: java$ mbox.txt had 4218 lines that matched java$
Exercise 2: Write a program to look for lines of the form
`New Revision: 39772`
and extract the number from each of the lines using a regular expression and the
findall() method. Compute the average of the numbers and print out the average.
Enter file:mbox.txt 38549.7949721 Enter file:mbox-short.txt 39756.9259259