11.E: Regular Expressions (Exercises)
- Page ID
- 3200
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