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 3.8+

pip install python-usernames

from python_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:

• whitelist: a case insensitive list of words that should be considered as always safe. Default: []

• blacklist: a case insensitive list of words that should be considered as unsafe. Default: []

• max_length: specify the maximun character a username can have. Default: None

• regex: regular expression string that must pass before the banned : words is checked.

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

• The-Big-Username-Blocklist
• Profanity-filter

• Let’s talk about usernames

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 :).

This project uses uv for dependency management and packaging.

1. Install uv:

   curl -LsSf https://astral.sh/uv/install.sh | sh

2. Clone the repository and sync dependencies:

   git clone https://github.com/theskumar/python-usernames.git
   cd python-usernames
   uv sync --all-groups

uv run pytest

uv run ruff check .
uv run black --check .

uv build

MIT