Level 6Exercise #139

Validate a username

Accept 3–15 characters containing letters, digits, or underscores only.

What you’ll practice

This Level 6 exercise focuses on re.fullmatch in the Professional curriculum. Solve the challenge prompt above using clear, idiomatic Python and the relevant language or standard-library tools.

Relevant Python reference: re — Regular expression operations.

Sample Test Cases

Example #1

Input:valid_username('ayan_7')

Output:True

Reference Solution

Reveal Reference Solution

def valid_username(name: str) -> bool:
    import re
    return re.fullmatch(r'[A-Za-z0-9_]{3,15}', name) is not None

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Validate a username

What you’ll practice

Sample Test Cases

Further Reading

Reference Solution