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Python library to validate usernames suitable for use in public facing applications.

Project description

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Python library to validate usernames suitable for use in public facing applications where use can choose login names and sub-domains.


  • Provides a default regex validator
  • Validates against list of banned words that should not be used as username.
  • Python 2.7, 3.4, 3.5, 3.6, 3.7 pypi


pip install python-usernames


from usernames import is_safe_username

>>> is_safe_username("jerk")
False  # contains one of the banned words

>>> is_safe_username("handsome!")
False  # contains non-url friendly `!`

is_safe_username takes the following optional arguments:

  • regex: regular expression string that must pass before the banned words is checked.
  • whitelist: a list of words that should be considered as always safe.
  • blacklist: a list of words that should be considered as unsafe.

The default regular expression is as follows:

^                       # beginning of string
(?!_$)                  # no only _
(?![-.])                # no - or . at the beginning
(?!.*[_.-]{2})          # no __ or _. or ._ or .. or -- inside
[a-zA-Z0-9_.-]+         # allowed characters, atleast one must be present
(?<![.-])               # no - or . at the end
$                       # end of string

Further Reading


Words like bigcock12 will validated just fine, only equality against the banned word lists is checked. We don’t try to be smart to avoid Scunthorpe problem. If you can come up with a algorithm/solution, please create an issue/pr :).



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