Descriptions¶

The galactic.descriptions module defines essential classes for representing characteristics:

Predicate for representing predicates
Description for representing descriptions
Equal for predicates whose calls to an individual will be retrieved by a equality with a value
Member for predicates whose calls to an individual will be retrieved by a membership test access
Absurd for predicates whose calls to an individual will be always false
Tautology for predicates whose calls to an individual will be always true

class galactic.descriptions.Predicate(*args: Any, description: Optional[Description] = None, **kwargs: Any)¶

Bases: galactic.characteristics.main.Characteristic

The Predicate class is used for characteristics whose call will return a boolean value.

class galactic.descriptions.Description(*args: galactic.characteristics.main.Characteristic, **_: Any)¶

Bases: object

The Description class is used to represent description spaces.

A description space must have a __call__() method able to compute the minimal descriptors for a collection of individuals.

space¶

A collection of characteristics.

Type: tuple

maximum: Optional[int] = None¶: The maximum number of characteristics that can reasonably be solved by this description.

minimum: Optional[int] = None¶: The minimum number of characteristics that can reasonably be solved by this description.

__init__(*args: galactic.characteristics.main.Characteristic, **_: Any) → None ¶

Initialise a description.

Parameters

*args (tuple) – A collection of Characteristic.

Raises

RuntimeError – If the number or arguments is not between the minimum and the maximum allowed.
TypeError – If an argument is not an instance of Characteristic

static combine(predicates: Iterator[galactic.descriptions.main.Predicate]) → Iterator[galactic.descriptions.main.Predicate]¶

Combine an iterator of predicates.

Parameters: predicates (Iterator[Predicate]) – An iterator of predicates
Returns: An iterator of predicates
Return type: Iterator[Predicate]

intersection(*predicates: galactic.descriptions.main.Predicate) → Iterator[galactic.descriptions.main.Predicate]¶

Compute the intersection of a collection of predicates for a particular description.

Parameters: *predicates (Predicate) – A collection of predicate
Returns: An iterator of predicates
Return type: Iterator[Predicate]

abstract __call__(individuals: Collection[Any]) → Iterator[galactic.descriptions.main.Predicate]¶

Compute the description of the individuals.

Keyword Arguments: individuals (Collection[Any]) – A collection of individuals
Returns: An iterator over a set of descriptors.
Return type: Iterator[Predicate]
Raises: TypeError – If the argument is not an instance of Collection[Any]

class galactic.descriptions.Member(*args: Any, description: Optional[Description] = None, **kwargs: Any)¶

Bases: galactic.descriptions.main.Predicate, galactic.characteristics.main.Named, galactic.characteristics.main.Composite

The Member class is used to represent member predicates.

name¶

The name hold by the instance.

Type: str

characteristics¶

The tuple of Characteristic instances hold by this instance.

Type: tuple

Example

>>> from galactic.descriptions import Member
>>> a = Member(name="x")
>>> print(a)
x
>>> a({"x"})
True
>>> a({})
False
>>>

class galactic.descriptions.Equal(*args: Any, description: Optional[Description] = None, **kwargs: Any)¶

Bases: galactic.descriptions.main.Predicate, galactic.characteristics.main.Composite, galactic.characteristics.main.Valued

The Equal class is used to represent the equality between a characteristic and a value.

characteristics¶

The characteristics (tuple of Characteristic instances) hold by this instance. This tuple contains only one Characteristic.

Type: tuple

data¶

The data hold by the instance.

Type: object

Example

>>> from galactic.characteristics import Key
>>> from galactic.descriptions import Equal
>>> a = Equal(Key(name="x"), data="hello")
>>> print(a)
x == hello
>>> a(1)
>>> a({})
>>> a({"x": "hello"})
True
>>> a({"x": "good bye"})
False

class galactic.descriptions.Absurd(*args: Any, description: Optional[Description] = None, **kwargs: Any)¶

Bases: galactic.descriptions.main.Predicate

The Absurd class represent the absurd class. It is always false.

class galactic.descriptions.Tautology(*args: Any, description: Optional[Description] = None, **kwargs: Any)¶

Bases: galactic.descriptions.main.Predicate

The Tautology class represent the tautology class. It is always true.