Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Python Regular Expressions in Python Introduction to Regular Expressions Sets

Sahar Nasiri
Sahar Nasiri
7,454 Points

Can we use "?" as a optional character

All the characters in the [] could exist or not, can't we write the print line like this:

print(re.findall(r'[-?\w?\d?+?.?]@[-?\w?\d?.?]', data))

1 Answer

Chris Freeman
Chris Freeman
Treehouse Moderator 68,094 Points

Square brackets [] define a character class (or set). Repeating letters within the brackets are redundant. Putting the question mark inside the class makes it also an optional character of the class. Without a question mark outside the class (and no other +, * or ? modifier) means exactly one character of the class.

So your proposed pattern would only find a single character followed by a @ followed by another single character.