GP Primitives

class Terminal(terminal, symbolic, ret_type)

Class that encapsulates a terminal primitive in an expression. Terminals can be either values or 0-arity functions.

Parameters:

  • terminal (TerminalTypes) – The terminal value or function.

  • symbolic (bool) – If True, the terminal is a string.

  • ret_type (type) – The return type of the terminal.

class Ephemeral

Class that encapsulates a terminal which value is set when the object is created. This is an abstract base class. When subclassing, a staticmethod named ‘func’ must be defined.

class Primitive(name, args, ret_type)

Class that encapsulates a primitive and when called with arguments it returns the Python code to call the primitive with the arguments.

Parameters:

  • name (str) – The name of the primitive.

  • args (list) – The list of arguments of the primitive.

  • ret_type (type) – The return type of the primitive.

class PrimitiveTree(content)

Tree specifically formatted for the optimization of genetic programming operations. This class is a subclass of ‘list’, where the nodes are appended, or are assumed to have been appended, when creating an object of this class with a list of primitives and terminals. The nodes appended to the tree are required to have the ‘arity’ attribute, which defines the arity of the primitive.

Parameters:

content (Iterable) – List of primitives and terminals to be added to the tree.

classmethod from_string(string, prim_set)

Converts a string expression into a PrimitiveTree given a PrimitiveSet p_set. The primitive set needs to contain every primitive present in the expression.

Parameters:

  • string (str) – String representation of a Python expression.

  • prim_set (PrimitiveSetTyped) – Primitive set from which primitives are selected.

Returns:

PrimitiveTree populated with the deserialized primitives.

Return type:

PrimitiveTree

search_subtree(begin)

Returns a slice object that corresponds to the range of values that defines the subtree which has the element with index ‘begin’ as its root.

Parameters:

begin (int) – Index of the root of the subtree.

Returns:

Slice object that corresponds to the range of values that defines the subtree.

Return type:

slice

property height

The height of the tree or the depth of the deepest node.

property root

The root of the tree (element 0 in the list).

class PrimitiveSet(name, arity, prefix='ARG')

Subclass of ‘PrimitiveSetTyped’ without the type definition.

Parameters:

  • name (str) – The name of the primitive set.

  • arity (int) – The arity of the primitive set.

  • prefix (str) – The prefix of the primitive set.

add_primitive(primitive, arity, name=None, *_, **__)

Adds a primitive to the set.

Parameters:

  • primitive (Callable) – Callable object or a function.

  • in_types – List of primitives arguments’ type.

  • ret_type – Type returned by the primitive.

  • name (str) – Alternative name for the primitive instead of its __name__ attribute.

Returns:

Nothing.

Return type:

None

add_terminal(terminal, name=None, *_, **__)

Adds a terminal to the set.

Parameters:

  • terminal (Any) – Callable object or a function.

  • ret_type – Type returned by the terminal.

  • name (str) – Alternative name for the terminal instead of its __name__ attribute.

Returns:

Nothing.

Return type:

None

add_ephemeral_constant(name, ephemeral, *_, **__)

Adds an ephemeral constant to the set. An ephemeral constant is a function without arguments that returns a random value. The value is immutable, but unique for each Tree.

Parameters:

  • ephemeral (Callable) – Callable object or a function.

  • ret_type – Type returned by the ephemeral.

  • name (str) – Name of this ephemeral type.

Returns:

Nothing.

Return type:

None

class PrimitiveSetTyped(name, in_types, ret_type, prefix='ARG')

Class that contains the primitives which can be used to solve a Strongly Typed GP problem.

Parameters:

  • name (str) – The name of the primitive set.

  • in_types (list) – The list of input types.

  • ret_type (type) – The return type.

  • prefix (str) – The prefix of the primitive set.

add_primitive(primitive, in_types, ret_type, name=None)

Adds a primitive to the set.

Parameters:

  • primitive (Callable) – Callable object or a function.

  • in_types (list) – List of primitives arguments’ type.

  • ret_type (type) – Type returned by the primitive.

  • name (str) – Alternative name for the primitive instead of its __name__ attribute.

Returns:

Nothing.

Return type:

None

add_terminal(terminal, ret_type, name=None)

Adds a terminal to the set.

Parameters:

  • terminal (Callable) – Callable object or a function.

  • ret_type (type) – Type returned by the terminal.

  • name (str) – Alternative name for the terminal instead of its __name__ attribute.

Returns:

Nothing.

Return type:

None

add_ephemeral_constant(name, ephemeral, ret_type)

Adds an ephemeral constant to the set. An ephemeral constant is a function without arguments that returns a random value. The value is immutable, but unique for each Tree.

Parameters:

  • ephemeral (Callable) – Callable object or a function.

  • ret_type (type) – Type returned by the ephemeral.

  • name (str) – Name of this ephemeral type.

Returns:

Nothing.

Return type:

None

add_adf(prim_set)

Adds an Automatically Defined Function (ADF) to the set.

Parameters:

prim_set (PrimitiveSetTyped) – PrimitiveSetTyped instance containing the primitives with which the ADF can be built.

Returns:

Nothing.

Return type:

None

rename_arguments(**kwargs)

Renames the arguments in self with new names from kwargs.

Parameters:

kwargs – Dictionary of new names for the arguments.

Returns:

Nothing.

Return type:

None

property terminal_ratio

The ratio between the quantity of terminals and the quantity of all the other kinds of primitives.