Python and Regex: Problem with re findall()

Question

This is a project found @ https://automatetheboringstuff.com/2e/chapter7/ It searches text on the clipboard for phone numbers and emails then copy the results to the clipboard again.

If I understood it correctly, when the regular expression contains groups, the findall() function returns a list of tuples. Each tuple would contain strings matching each regex group.

Now this is my problem: the regex on phoneRegex as far as i can tell contains only 6 groups (numbered on the code) (so i would expect tuples of length 6)

But when I print the tuples i get tuples of length 9

('800-420-7240', '800', '-', '420', '-', '7240', '', '', '')
('415-863-9900', '415', '-', '863', '-', '9900', '', '', '')
('415-863-9950', '415', '-', '863', '-', '9950', '', '', '')

What am i missing?

#! python3
# phoneAndEmail.py - Finds phone numbers and email addresses on the clipboard.

import pyperclip, re

phoneRegex = re.compile(r'''(
    (\d{3}|\(\d{3}\))?                # area code (first group?)0
    (\s|-|\.)?                        # separator               1
    (\d{3})                           # first 3 digits          2
    (\s|-|\.)                         # separator               3
    (\d{4})                           # last 4 digits           4
    (\s*(ext|x|ext.)\s*(\d{2,5}))?    # extension               5
    )''', re.VERBOSE)

# Create email regex.
emailRegex = re.compile(r'''(
   [a-zA-Z0-9._%+-]+      # username
   @                      # @ symbol
   [a-zA-Z0-9.-]+         # domain name
    (\.[a-zA-Z]{2,4})     # dot-something
    )''', re.VERBOSE)

text = str(pyperclip.paste())

matches = []
for groups in phoneRegex.findall(text):
    print(groups)
    phoneNum = '-'.join([groups[1], groups[3], groups[5]])
    if groups[8] != '':
        phoneNum += ' x' + groups[8]
    matches.append(phoneNum)
for groups in emailRegex.findall(text):
    matches.append(groups[0])

    # Copy results to the clipboard.
if len(matches) > 0:
    pyperclip.copy('\n'.join(matches))
    print('Copied to clipboard:')
    print('\n'.join(matches))
else:
    print('No phone numbers or email addresses found.')

jdaz · Accepted Answer · 2020-08-05T18:53:38.577

Anything in parentheses will become a capturing group (and add one to the length of the re.findall tuple) unless you specify otherwise. To turn a sub-group into a non-capturing group, add ?: just inside the parentheses:

phoneRegex = re.compile(r'''(
    (\d{3}|\(\d{3}\))?                 
    (\s|-|\.)?                        
    (\d{3})                           
    (\s|-|\.)                         
    (\d{4})                              
    (\s*(?:ext|x|ext.)\s*(?:\d{2,5}))?    # <---
    )''', re.VERBOSE)

You can see the extension part was adding two additional capturing groups. With this updated version, you will have 7 items in your tuple. There are 7 instead of 6 because the entire string is matched as well.

The regex could be better, too. This is cleaner and will match more cases with the re.IGNORECASE flag:

phoneRegex = re.compile(r'''(
    (\(?\d{3}\)?)                
    ([\s.-])?                        
    (\d{3})                           
    ([\s.-])                         
    (\d{4})                              
    \s*  # don't need to capture whitespace
    ((?:ext\.?|x)\s*(?:\d{1,5}))?
    )''', re.VERBOSE | re.IGNORECASE)

Python and Regex: Problem with re findall()

1 Answers1