Username in PY
Validate usernames that are 3–16 characters long and contain only letters, digits, underscores, and hyphens.
Try it in the PY tester →Pattern
regexPY
^[a-zA-Z0-9_\-]{3,16}$Python (re) code
pyPython
import re
pattern = re.compile(r"^[a-zA-Z0-9_\-]{3,16}$")
input_text = "john_doe"
for m in pattern.finditer(input_text):
print(m.group(0))Stdlib `re` module — no third-party dependency. Works on Python 3.6+.
How the pattern works
^ and $ anchor to the full string. The character class [a-zA-Z0-9_\-] allows letters (upper and lower), digits, underscores, and hyphens. {3,16} enforces the length range most platforms use for usernames.
Examples
Input
john_doeMatches
john_doe
Input
user-123Matches
user-123
Input
abNo match
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