{"id":3178,"library":"nulltype","title":"NullType Sentinels","description":"nulltype is a Python library (current version 2.3.1) that provides custom null values and sentinels, distinct from Python's built-in `None`, `False`, or `True`. It helps represent different states of 'emptiness' or 'undefined' values, such as `Passthrough`, `Prohibited`, or `Undefined`, without overloading standard Python nullish objects. The library aims to simplify code by allowing robust handling of potentially missing data in a consistent way. The last release was in June 2018, indicating a maintenance phase with infrequent updates.","status":"maintenance","version":"2.3.1","language":"en","source_language":"en","source_url":"https://github.com/dgorissen/nulltype","tags":["utility","null-object","sentinel","data-handling","empty"],"install":[{"cmd":"pip install nulltype","lang":"bash","label":"Install stable version"}],"dependencies":[],"imports":[{"symbol":"NullType","correct":"from nulltype import NullType"},{"symbol":"Empty","correct":"from nulltype import Empty"},{"symbol":"Null","correct":"from nulltype import Null"},{"symbol":"Nothing","correct":"from nulltype import Nothing"}],"quickstart":{"code":"from nulltype import NullType, Empty, Nothing, Null\n\n# Create a custom null type\nUndefined = NullType('Undefined')\n\n# Test common Pythonic behaviors\nassert bool(Undefined) is False\nassert len(Undefined) == 0\nassert list(Undefined) == []\n\n# Accessing attributes, items, or calling a NullType instance\n# By default, for custom NullTypes, attribute/call access returns Empty, and item access returns Nothing.\n# For predefined sentinels like Empty, these operations return themselves.\nassert Undefined.some_attribute is Empty\nassert Undefined[22] is Nothing\nassert Undefined(\"hey\", 12) is Empty\n\n# Using pre-defined sentinels\nassert Empty.any_attr is Empty\nassert Nothing[0] is Nothing\nassert Null() is Null\n\nprint(\"NullType examples ran successfully!\")","lang":"python","description":"Demonstrates how to create a custom `NullType` and its behavior when subjected to common Python operations (boolean evaluation, length, iteration, attribute access, item access, and calls). It also shows the use of the pre-defined `Empty`, `Nothing`, and `Null` sentinels."},"warnings":[{"fix":"Rely on the convention of creating each NullType once, typically at module level, to ensure single instance behavior.","message":"NullType instances are intended to be singletons (one per program) but their uniqueness is not strictly enforced. While this is rarely an issue in practice, users should be mindful that multiple instances with the same name could technically exist if not careful with usage patterns.","severity":"gotcha","affected_versions":"2.0.0 and later"},{"fix":"Test your application's usage of `nulltype` thoroughly when upgrading to newer Python environments. Consider alternatives if explicit compatibility with the latest Python features or type hinting is critical.","message":"The library was last released in 2018 and was explicitly tested up to Python 3.7 pre-release. While generally compatible with newer Python versions, it is not actively tested against Python 3.8+ versions. Users on recent Python versions should verify compatibility, especially concerning subtle changes in built-in behaviors or type hinting.","severity":"gotcha","affected_versions":"Python 3.8 and later (untested)"}],"env_vars":null,"last_verified":"2026-04-11T00:00:00.000Z","next_check":"2026-07-10T00:00:00.000Z"}