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Python Regular Expressions in Python Introduction to Regular Expressions Negation

Flore W
Flore W
4,744 Points
Posted by Flore W
Flore W
4,744 Points

Negation Regex I need help with \b

Here is a reminder of Kenneth's code:

import re
names_file = open('names.txt', encoding = 'utf-8')
data = names_file.read()
names_file.close()

print(re.findall(r'''
    \b@[-\w\d.]*
    [^gov\t]+
    \b
''', data, re.X|re.I))

This gives a result of the @ part of email addresses, excluding "gov", a few examples here:

['@teamtreehouse.com', '@camelot.co.uk', '@spain.']

I have tried taking out the two '\b' and it gives the result:

['@kennethlove\nMcFarland, ', '@potus44\nChalkey, Andrew']

I don't understand why taking out the \b will mean that I find combinations including '\n', ',' and ' ' - none of those are contained in my @[-\w.+]*, so why would those appear?

1 Answer

Saikat Chowdhury
Saikat Chowdhury
3,128 Points
Saikat Chowdhury
Saikat Chowdhury
3,128 Points

Hi Flore, /b is looking for word boundary or edges of the word define by white spaces. Here It will check start and end of the string.

my thinking is , when you remove two \b from your regex script then it started searching twitter records. And Twitter record has @ . Because of + sign it goes to next line . And you are getting below result eg. ['@kennethlove\nMcFarland, ', '@potus44\nChalkey, Andrew']

if you remove + sign from [^gov\t]\b then it will stay on same line, even you remove \b from your regex script.

Regards, Saikat