Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python Regular Expressions in Python Introduction to Regular Expressions Negated Numbers

Marzoog AlGhazwi
Marzoog AlGhazwi
15,796 Points
Posted by Marzoog AlGhazwi
Marzoog AlGhazwi
15,796 Points

why it work with the '8' but with it didn't ??!

Can any one expline why its working that way !

negate.py 
import re

string = '1234567890'

good_numbers = re.findall(r'''
    \d
    [^5678]+                         
''', string, re.X)

1 Answer

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

The "\d" token matches any digit, so without the "8" you get two pieces, "1234" and then "7890" because it "7" is matched by the "\d".

But when you add "8" to the excluded digits, then "7890" no longer matches, so you get "890" where the "8" matches the "\d":.

A more conventional solution might use just one character class without the "any digit" preceding it.