Missing

class brainstate.typing.Missing

Sentinel class to represent missing or unspecified values.

This class is used as a default value when None has semantic meaning and you need to distinguish between “None was passed” and “nothing was passed”.

Examples

>>> _MISSING = Missing()
>>>
>>> def function_with_optional_param(value: Union[int, None, Missing] = _MISSING):
...     if value is _MISSING:
...         print("No value provided")
...     elif value is None:
...         print("None was explicitly provided")
...     else:
...         print(f"Value: {value}")
>>>
>>> function_with_optional_param()        # "No value provided"
>>> function_with_optional_param(None)    # "None was explicitly provided"
>>> function_with_optional_param(42)      # "Value: 42"