blueprints.thing.base module#

Note

If you found yourself here not being a dev, you should probably skip this section or look up the correspinging docs page of the Thing you were looking after for which this module only implements its corresponding mirror types. A link to the docs page is to be found in the Types doc string.

class blueprints.thing.base.BaseThing[source]#

Bases: ThingType

BaseThing implements the basic attributes that are used by all Things.

All Things have certain attributes that are included in the mujoco XML construction. The names of those attributes can be obtained from the _MUJOCO_ATTR property which is dictionary with attribute names as keys and the types their value will have in the Thing instance. If a new Thing class is defined that inherits from BaseThing that introduces new attributes to be written to xml, they can be added by defining a class property _NEW_MUJOCO_ATTR in the same structure that _MUJOCO_ATTR is defined. _MUJOCO_ATTR then simply aggregates the new additions from _NEW_MUJOCO_ATTR. If a new Thing class inherits a mujoco attribute, that is no longer used, it can be deleted from _MUJOCO_ATTR by defining it in a class property _DEL_MUJOCO_ATTR, must be a set of the names to be detached.

When a Thing is copied, all attributes needed to reconstruct it are retrieved to create a new instance. For this the blueprints.type.ThingType._BLUEPRINT_ATTR property is used. New attributes that are feed into the inheriting Thing.__init__ are registered in the class property _NEW_BLUEPRINTS_ATTR and old attributes that are no longer used are registered in _DEL_BLUEPRINTS_ATTR. Their structures are analogous to the _MUJOCO_ATTR.

If a Thing gets copied all attributes necessary to instantiate the copy are themselves copied to ensure that the Thing and its copy do not share a reference to the same object in any attribute. However, if an attribute is added to blueprints.type.ThingType._NO_COPY_VALS it is not copied. New attributes to be excluded from being copied can be added by setting the class property _NEW_NO_COPY_VALS to the classes Type as a set of attribute names.

If a Thing is reconstructed from an xml string, some attribute in the xml tag are not attributes of the Thing class. For example, a geom xml tag will have a type defining its shape <geom type='sphere'> but the corresponding blueprints.geoms.Sphere class specifies the type only implicitly in its name. To retrieve the correct class in reconstruction from xml then, those implicit attributes are gathered in the class property blueprints.type.ThingType._DERIVED_ATTR to explicitly derived later. Adding new attributes to it is done by setting the class property _NEW_DERIVED_ATTR of the Things Type as a set of attribute names.

To ensure readability of the resulting xml, attributes that are set to their mujoco defaults are omitted from the xml representations (even though all attributes are set in the Thing instance). To check whether an attributes value equals its default, it can be obtained from the _DEFAULT_VALS class property, which is structured as a dictionary of attribute names as keys and their defaults as values. New default values of inheriting classes are added analogously to the previous cases by setting them in a class property _NEW_DEFAULT_VALS of its Type.

Parameters:

  • name (str | None, optional) – This is the name for the object specified by the user. It differs from other user specified properties, in that it might be altered without the users knowledge to resolve name conflicts.

  • parent (blue.NodeThingType | None, optional) – The parent to which the Thing is attach, if it unattached parent is None.

  • **kwargs – The aggregation of keyword arguments that have not yet been caught by other inheriting Things __init__ are not used and serve as a dummy variable.

ID#

Each Thing has a unique ID that is gets on initialization from the global REGISTER.

Type:

int

__init__(name=None, parent=None, **kwargs)[source]#
Parameters:

  • name (str | None, optional) – This is the name for the object specified by the user. It differs from other user specified properties, in that it might be altered without the users knowledge to resolve name conflicts.

  • parent (blue.NodeThingType | None, optional) – The parent to which the Thing is attach, if it unattached parent is None.

  • **kwargs – The aggregation of keyword arguments that have not yet been caught by other inheriting Things __init__ are not used and serve as a dummy variable.

copy(**kwargs)[source]#

This method constructs a copy of the Thing with possible alterations to its attributes as specified in kwargs.

Parameters:

**kwargs – Keyword arguments are passed to the Thing.__init__ to replace the attributes of the current Thing from which copy is called.

Returns:

A new instance of the Thing

Return type:

blue.ThingType

property root: ThingType#

The root attribute is immutable and changes only if the structure of the kinematic tree is altered.

Returns:

Retrieves the root of the kinematic tree the Thing in part of, possibly the Thing itself if it has no parent.

Return type:

blue.ThingType

property path: list#

The path attribute is immutable and changes only if the structure of the kinematic tree is altered.

Returns:

Retrieves a list of all Things that lead from the Thing itself to its root.

Return type:

list

property parent: ThingType | None#

If the Thing is attach to a blueprints.World it is informed that its child was altered such that on the next method call on the World, that require the current build, that it needs to rebuild.

Parameters:

  • attr (str) – The name of the attribute to be set.

  • value (object) – The value assigned to the attribute.

property name: str#

The returned name might differ from the user specification by an enumerations scheme that is applied if two Things of the same type in a kinematic tree share the same name.

Returns:

possibly extended name of the Thing

Return type:

str