Python Programming for Raspberry Pi, Sams Teach Yourself in 24 Hours

After the phone exchange number, you must again match either a space, a dash, or a

dot:

( |-|\.)

Then to finish things off, you must match the four-digit local phone extension at the

end of the string:

[0-9]{4}$

Putting the entire pattern together results in this:

Click here to view code image

^\(?[2-9][0-9]{2}\)?(| |-|\.)[0-9]{3}( |-|\.)[0-9]{4}$

2. Now that you have a regular expression, plug it into your code by opening a text
   editor and entering this code:
   Click here to view code image
   #!/usr/bin/python3

import re

pattern = re.compile(r'^\(?[2-9][0-9]{2}\)?(| |-|\.)[0-9]{3}( |-|\.)[0-9]

{4}$')

while(True):

phone = input('Enter a phone number:')

if (phone == 'exit'):

break

if (pattern.search(phone)):

print('That is a valid phone number')

else:

print('Sorry, that is not a valid phone number')

print('Thanks for trying our program')

3. Save the file and exit the text editor.


4. Run the file from the Raspberry Pi command prompt or the LXTerminal program in
   your window:
   Click here to view code image
   pi@raspberrypi ~ $ python3 script1601.py
   Enter a phone number:(555)555-1234
   That is a valid phone number
   Enter a phone number:333.123.4567
   That is a valid phone number
   Enter a phone number: 1234567890
   Sorry, that is not a valid phone number
   Enter a phone number:exit
   Thanks for trying our program
   pi@raspberrypi ~ $
   This is all there is to it! The script matches the input value against the regular
   expression pattern and displays the appropriate message.

Summary

If you manipulate data in Python scripts, you need to become familiar with regular expressions. A
regular expression defines a pattern template that’s used to filter text in a string value. The pattern