# Copyright 2018 The dm_control Authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

# ============================================================================

"""Classes to represent MJCF elements in the object model."""

import collections

import copy

import os

import sys

from dm_control.mjcf import attribute as attribute_types

from dm_control.mjcf import base

from dm_control.mjcf import constants

from dm_control.mjcf import copier

from dm_control.mjcf import debugging

from dm_control.mjcf import namescope

from dm_control.mjcf import schema

from dm_control.mujoco.wrapper import util

from lxml import etree

import numpy as np

_raw_property = property # pylint: disable=invalid-name

_UNITS = ('K', 'M', 'G', 'T', 'P', 'E')

def _to_bytes(value_str):

"""Converts a `str` value representing a size in bytes to `int`.

Args:

value_str: `str` value to be converted.

Returns:

`int` corresponding size in bytes.

Raises:

ValueError: if the `str` value passed has an unsupported unit.

"""

if value_str.isdigit():

value_int = int(value_str)

else:

value_int = int(value_str[:-1])

unit = value_str[-1].upper()

if unit not in _UNITS:

raise ValueError(

f'unit of `size.memory` should be one of [{", ".join(_UNITS)}], got'

f' {unit}')

power = 10 * (_UNITS.index(unit) + 1)

value_int *= 2**power

return value_int

def _max_bytes(first, second):

return str(max(_to_bytes(first), _to_bytes(second)))

_CONFLICT_BEHAVIOR_FUNC = {'min': min, 'max': max, 'max_bytes': _max_bytes}

def property(method): # pylint: disable=redefined-builtin

"""Modifies `@property` to keep track of any `AttributeError` raised.

Our `Element` implementations overrides the `__getattr__` method. This does

not interact well with `@property`: if a `property`'s code is buggy so as to

raise an `AttributeError`, then Python would silently discard it and redirect

to our `__getattr__` instead, leading to an uninformative stack trace. This

makes it very difficult to debug issues that involve properties.

To remedy this, we modify `@property` within this module to store any

`AttributeError` raised within the respective `Element` object. Then, in our

`__getattr__` logic, we could re-raise it to preserve the original stack

trace.

The reason that this is not implemented as a different decorator is that we

could accidentally use @property on a new method. This would work fine until

someone triggers a subtle bug. This is when a proper trace would be most

useful, but we would still end up with a strange undebuggable stack trace

anyway.

Note that at the end of this module, we have a `del property` to prevent this

override from being broadcasted externally.

Args:

method: The method that is being decorated.

Returns:

A `property` corresponding to the decorated method.

"""

def _mjcf_property(self):

try:

return method(self)

except:

_, err, tb = sys.exc_info()

err_with_next_tb = err.with_traceback(tb.tb_next)

if isinstance(err, AttributeError):

self._last_attribute_error = err_with_next_tb # pylint: disable=protected-access

raise err_with_next_tb # pylint: disable=raise-missing-from

return _raw_property(_mjcf_property)

def _make_element(spec, parent, attributes=None):

"""Helper function to generate the right kind of Element given a spec."""

if (spec.name == constants.WORLDBODY

or (spec.name == constants.SITE

and (parent.tag == constants.BODY

or parent.tag == constants.WORLDBODY))):

return _AttachableElement(spec, parent, attributes)

elif isinstance(parent, _AttachmentFrame):

return _AttachmentFrameChild(spec, parent, attributes)

elif spec.name == constants.DEFAULT:

return _DefaultElement(spec, parent, attributes)

elif spec.name == constants.ACTUATOR:

return _ActuatorElement(spec, parent, attributes)

else:

return _ElementImpl(spec, parent, attributes)

_DEFAULT_NAME_FROM_FILENAME = frozenset(['mesh', 'hfield', 'texture'])

class _ElementImpl(base.Element):

"""Actual implementation of a generic MJCF element object."""

__slots__ = ['__weakref__', '_spec', '_parent', '_attributes', '_children',

'_own_attributes', '_attachments', '_is_removed', '_init_stack',

'_is_worldbody', '_cached_namescope', '_cached_root',

'_cached_full_identifier', '_cached_revision',

'_last_attribute_error']

def __init__(self, spec, parent, attributes=None):

attributes = attributes or {}

# For certain `asset` elements the `name` attribute can be omitted, in which

# case the name will be the filename without the leading path and extension.

# See http://www.mujoco.org/book/XMLreference.html#asset.

if ('name' not in attributes

and 'file' in attributes

and spec.name in _DEFAULT_NAME_FROM_FILENAME):

_, filename = os.path.split(attributes['file'])

basename, _ = os.path.splitext(filename)

attributes['name'] = basename

self._spec = spec

self._parent = parent

self._attributes = collections.OrderedDict()

self._own_attributes = None

self._children = []

self._attachments = collections.OrderedDict()

self._is_removed = False

self._is_worldbody = (self.tag == 'worldbody')

if self._parent:

self._cached_namescope = self._parent.namescope

self._cached_root = self._parent.root

self._cached_full_identifier = ''

self._cached_revision = -1

self._last_attribute_error = None

if debugging.debug_mode():

self._init_stack = debugging.get_current_stack_trace()

with debugging.freeze_current_stack_trace():

for child_spec in self._spec.children.values():

if not (child_spec.repeated or child_spec.on_demand):

self._children.append(_make_element(spec=child_spec, parent=self))

if constants.DCLASS in attributes:

attributes[constants.CLASS] = attributes[constants.DCLASS]

del attributes[constants.DCLASS]

for attribute_name in attributes.keys():

self._check_valid_attribute(attribute_name)

for attribute_spec in self._spec.attributes.values():

value = None

# Some Reference attributes refer to a namespace that is specified

# via another attribute. We therefore have to set things up for

# the additional indirection.

if attribute_spec.type is attribute_types.Reference:

reference_namespace = (

attribute_spec.other_kwargs['reference_namespace'])

if reference_namespace.startswith(

constants.INDIRECT_REFERENCE_NAMESPACE_PREFIX):

attribute_spec = copy.deepcopy(attribute_spec)

namespace_attrib_name = reference_namespace[

len(constants.INDIRECT_REFERENCE_NAMESPACE_PREFIX):]

attribute_spec.other_kwargs['reference_namespace'] = (

self._attributes[namespace_attrib_name])

if attribute_spec.name in attributes:

value = attributes[attribute_spec.name]

try:

self._attributes[attribute_spec.name] = attribute_spec.type(

name=attribute_spec.name,

required=attribute_spec.required,

conflict_allowed=attribute_spec.conflict_allowed,

conflict_behavior=attribute_spec.conflict_behavior,

parent=self, value=value, **attribute_spec.other_kwargs)

except:

# On failure, clear attributes already created

for attribute_obj in self._attributes.values():

attribute_obj._force_clear() # pylint: disable=protected-access

# Then raise a meaningful error

err_type, err, tb = sys.exc_info()

raise err_type( # pylint: disable=raise-missing-from

f'during initialization of attribute {attribute_spec.name!r} of '

f'element <{self._spec.name}>: {err}').with_traceback(tb)

def get_init_stack(self):

"""Gets the stack trace where this element was first initialized."""

if debugging.debug_mode():

return self._init_stack

def get_last_modified_stacks_for_all_attributes(self):

"""Gets a dict of stack traces where each attribute was last modified."""

return collections.OrderedDict(

[(name, self._attributes[name].last_modified_stack)

for name in self._spec.attributes])

def is_same_as(self, other):

"""Checks whether another element is semantically equivalent to this one.

Two elements are considered equivalent if they have the same

specification (i.e. same tag appearing in the same context), the same

attribute values, and all of their children are equivalent. The ordering

of non-repeated children is not important for this comparison, while

the ordering of repeated children are important only amongst the same

type* of children. In other words, for two bodies to be considered

equivalent, their child sites must appear in the same order, and their

child geoms must appear in the same order, but permutations between sites

and geoms are disregarded. (The only exception is in tendon definition,

where strict ordering of all children is necessary for equivalence.)

*Note that the notion of "same type" in this function is very loose:

for example different actuator element subtypes are treated as separate

types when children ordering is considered. Therefore, two <actuator>

elements might be considered equivalent even though they result in different

orderings of `mjData.ctrl` when compiled. As it stands, this function

is designed primarily as a testing aid and should not be used to guarantee

that models are actually identical.

Args:

other: An `mjcf.Element`

Returns:

`True` if `other` element is semantically equivalent to this one.

"""

if other is None or other.spec != self._spec:

return False

for attribute_name in self._spec.attributes.keys():

attribute = self._attributes[attribute_name]

other_attribute = getattr(other, attribute_name)

if isinstance(attribute.value, base.Element):

if attribute.value.full_identifier != other_attribute.full_identifier:

return False

elif not np.all(attribute.value == other_attribute):

return False

if (self._parent and

self._parent.tag == constants.TENDON and

self._parent.parent == self.root):

return self._tendon_has_same_children_as(other)

else:

return self._has_same_children_as(other)

def _has_same_children_as(self, other):

"""Helper function to check whether another element has the same children.

See docstring for `is_same_as` for explanation about the treatment of

children ordering.

Args:

other: An `mjcf.Element`

Returns:

A boolean

"""

for child_name, child_spec in self._spec.children.items():

child = self.get_children(child_name)

other_child = getattr(other, child_name)

if not child_spec.repeated:

if ((child is None and other_child is not None) or

(child is not None and not child.is_same_as(other_child))):

return False

else:

if len(child) != len(other_child):

return False

else:

for grandchild, other_grandchild in zip(child, other_child):

if not grandchild.is_same_as(other_grandchild):

return False

return True

def _tendon_has_same_children_as(self, other):

return all(child.is_same_as(other_child)

for child, other_child

in zip(self.all_children(), other.all_children()))

def _alias_attributes_dict(self, other):

if self._own_attributes is None:

self._own_attributes = self._attributes

self._attributes = other

def _restore_attributes_dict(self):

if self._own_attributes is not None:

for attribute_name, attribute in self._attributes.items():

self._own_attributes[attribute_name].value = attribute.value

self._attributes = self._own_attributes

self._own_attributes = None

@property

def tag(self):

return self._spec.name

@property

def spec(self):

return self._spec

@property

def parent(self):

return self._parent

@property

def namescope(self):

return self._cached_namescope

@property

def root(self):

return self._cached_root

def prefixed_identifier(self, prefix_root):

if not self._spec.identifier and not self._is_worldbody:

return None

elif self._is_worldbody:

prefix = self.namescope.full_prefix(prefix_root=prefix_root)

return prefix or 'world'

else:

full_identifier = (

self._attributes[self._spec.identifier].to_xml_string(

prefix_root=prefix_root))

if full_identifier:

return full_identifier

else:

prefix = self.namescope.full_prefix(prefix_root=prefix_root)

prefix = prefix or constants.PREFIX_SEPARATOR

return prefix + self._default_identifier

@property

def full_identifier(self):

"""Fully-qualified identifier used for this element in the generated XML."""

if self.namescope.revision > self._cached_revision:

self._cached_full_identifier = self.prefixed_identifier(

prefix_root=self.namescope.root)

self._cached_revision = self.namescope.revision

return self._cached_full_identifier

@property

def _default_identifier(self):

"""The default identifier used if this element is not named by the user."""

if not self._spec.identifier:

return None

else:

siblings = self.root.find_all(self._spec.namespace,

exclude_attachments=True)

return '{separator}unnamed_{namespace}_{index}'.format(

separator=constants.PREFIX_SEPARATOR,

namespace=self._spec.namespace,

index=siblings.index(self))

def __dir__(self):

out_dir = set()

classes = (type(self),)

while classes:

super_classes = set()

for klass in classes:

out_dir.update(klass.__dict__)

super_classes.update(klass.__bases__)

classes = super_classes

out_dir.update(self._spec.children)

out_dir.update(self._spec.attributes)

if constants.CLASS in out_dir:

out_dir.remove(constants.CLASS)

out_dir.add(constants.DCLASS)

return sorted(out_dir)

def find(self, namespace, identifier):

"""Finds an element with a particular identifier.

This function allows the direct access to an arbitrarily deeply nested

child element by name, without the need to manually traverse through the

object tree. The `namespace` argument specifies the kind of element to

find. In most cases, this corresponds to the element's XML tag name.

However, if an element has multiple specialized tags, then the namespace

corresponds to the tag name of the most general element of that kind.

For example, `namespace='joint'` would search for `<joint>` and

`<freejoint>`, while `namespace='actuator'` would search for `<general>`,

`<motor>`, `<position>`, `<velocity>`, and `<cylinder>`.

Args:

namespace: A string specifying the namespace being searched. See the

docstring above for explanation.

identifier: The identifier string of the desired element.

Returns:

An `mjcf.Element` object, or `None` if an element with the specified

identifier is not found.

Raises:

ValueError: if either `namespace` or `identifier` is not a string, or if

`namespace` is not a valid namespace.

"""

if not isinstance(namespace, str):

raise ValueError(

'`namespace` should be a string: got {!r}'.format(namespace))

if not isinstance(identifier, str):

raise ValueError(

'`identifier` should be a string: got {!r}'.format(identifier))

if namespace not in schema.FINDABLE_NAMESPACES:

raise ValueError('{!r} is not a valid namespace. Available: {}.'.format(

namespace, schema.FINDABLE_NAMESPACES))

if constants.PREFIX_SEPARATOR in identifier:

scope_name = identifier.split(constants.PREFIX_SEPARATOR)[0]

try:

attachment = self.namescope.get('attached_model', scope_name)

found_element = attachment.find(

namespace, identifier[(len(scope_name) + 1):])

except (KeyError, ValueError):

found_element = None

else:

try:

found_element = self.namescope.get(namespace, identifier)

except KeyError:

found_element = None

if found_element and self._parent:

next_parent = found_element.parent

while next_parent and next_parent != self:

next_parent = next_parent.parent

if not next_parent:

found_element = None

return found_element

def find_all(self, namespace,

immediate_children_only=False, exclude_attachments=False):

"""Finds all elements of a particular kind.

The `namespace` argument specifies the kind of element to

find. In most cases, this corresponds to the element's XML tag name.

However, if an element has multiple specialized tags, then the namespace

corresponds to the tag name of the most general element of that kind.

For example, `namespace='joint'` would search for `<joint>` and

`<freejoint>`, while `namespace='actuator'` would search for `<general>`,

`<motor>`, `<position>`, `<velocity>`, and `<cylinder>`.

Args:

namespace: A string specifying the namespace being searched. See the

docstring above for explanation.

immediate_children_only: (optional) A boolean, if `True` then only

the immediate children of this element are returned.

exclude_attachments: (optional) A boolean, if `True` then elements

belonging to attached models are excluded.

Returns:

A list of `mjcf.Element`.

Raises:

ValueError: if `namespace` is not a valid namespace.

"""

if namespace not in schema.FINDABLE_NAMESPACES:

raise ValueError('{!r} is not a valid namespace. Available: {}'.format(

namespace, schema.FINDABLE_NAMESPACES))

out = []

children = self._children if exclude_attachments else self.all_children()

for child in children:

if (namespace == child.spec.namespace or

# Direct children of attachment frames have custom namespaces of the

# form "joint@attachment_frame_<id>".

child.spec.namespace and child.spec.namespace.startswith(

namespace + constants.NAMESPACE_SEPARATOR) or

# Attachment frames are considered part of the "body" namespace.

namespace == constants.BODY and isinstance(child, _AttachmentFrame)):

out.append(child)

if not immediate_children_only:

out.extend(child.find_all(namespace,

exclude_attachments=exclude_attachments))

return out

def enter_scope(self, scope_identifier):

"""Finds the root element of the given scope and returns it.

This function allows the access to a nested scope that is a child of this

element. The `scope_identifier` argument specifies the path to the child

scope element.

Args:

scope_identifier: The path of the desired scope element.

Returns:

An `mjcf.Element` object, or `None` if a scope element with the

specified path is not found.

"""

if constants.PREFIX_SEPARATOR in scope_identifier:

scope_name = scope_identifier.split(constants.PREFIX_SEPARATOR)[0]

try:

attachment = self.namescope.get('attached_model', scope_name)

except KeyError:

return None

scope_suffix = scope_identifier[(len(scope_name) + 1):]

if scope_suffix:

return attachment.enter_scope(scope_suffix)

else:

return attachment

else:

try:

return self.namescope.get('attached_model', scope_identifier)

except KeyError:

return None

def _check_valid_attribute(self, attribute_name):

if attribute_name not in self._spec.attributes:

raise AttributeError(

'{!r} is not a valid attribute for <{}>'.format(

attribute_name, self._spec.name))

def _get_attribute(self, attribute_name):

self._check_valid_attribute(attribute_name)

return self._attributes[attribute_name].value

def get_attribute_xml_string(self,

attribute_name,

prefix_root=None,

*,

precision=constants.XML_DEFAULT_PRECISION,

zero_threshold=0):

self._check_valid_attribute(attribute_name)

return self._attributes[attribute_name].to_xml_string(

prefix_root, precision=precision, zero_threshold=zero_threshold)

def get_attributes(self):

fix_attribute_name = (

lambda name: constants.DCLASS if name == constants.CLASS else name)

return collections.OrderedDict(

[(fix_attribute_name(name), self._get_attribute(name))

for name in self._spec.attributes.keys()

if self._get_attribute(name) is not None])

def _set_attribute(self, attribute_name, value):

self._check_valid_attribute(attribute_name)

self._attributes[attribute_name].value = value

self.namescope.increment_revision()

def set_attributes(self, **kwargs):

if constants.DCLASS in kwargs:

kwargs[constants.CLASS] = kwargs[constants.DCLASS]

del kwargs[constants.DCLASS]

old_values = []

with debugging.freeze_current_stack_trace():

for attribute_name, new_value in kwargs.items():

old_value = self._get_attribute(attribute_name)

try:

self._set_attribute(attribute_name, new_value)

old_values.append((attribute_name, old_value))

except:

# On failure, restore old attribute values for those already set.

for name, old_value in old_values:

self._set_attribute(name, old_value)

# Then raise a meaningful error.

err_type, err, tb = sys.exc_info()

raise err_type( # pylint: disable=raise-missing-from

f'during assignment to attribute {attribute_name!r} of '

f'element <{self._spec.name}>: {err}').with_traceback(tb)

def _remove_attribute(self, attribute_name):

self._check_valid_attribute(attribute_name)

self._attributes[attribute_name].clear()

self.namescope.increment_revision()

def _check_valid_child(self, element_name):

try:

return self._spec.children[element_name]

except KeyError:

raise AttributeError( # pylint: disable=raise-missing-from

'<{}> is not a valid child of <{}>'

.format(element_name, self._spec.name))

def get_children(self, element_name):

child_spec = self._check_valid_child(element_name)

if child_spec.repeated:

return _ElementListView(spec=child_spec, parent=self)

else:

for child in self._children:

if child.tag == element_name:

return child

if child_spec.on_demand:

return None

else:

raise RuntimeError(

'Cannot find the non-repeated child <{}> of <{}>. '

'This should never happen, as we pre-create these in __init__. '

'Please file an bug report. Thank you.'

.format(element_name, self._spec.name))

def add(self, element_name, **kwargs):

"""Add a new child element to this element.

Args:

element_name: The tag of the element to add.

**kwargs: Attributes of the new element being created.

Raises:

ValueError: If the 'element_name' is not a valid child, or if an invalid

attribute is specified in `kwargs`.

Returns:

An `mjcf.Element` corresponding to the newly created child element.

"""

return self.insert(element_name, position=None, **kwargs)

def insert(self, element_name, position, **kwargs):

"""Add a new child element to this element.

Args:

element_name: The tag of the element to add.

position: Where to insert the new element.

**kwargs: Attributes of the new element being created.

Raises:

ValueError: If the 'element_name' is not a valid child, or if an invalid

attribute is specified in `kwargs`.

Returns:

An `mjcf.Element` corresponding to the newly created child element.

"""

child_spec = self._check_valid_child(element_name)

if child_spec.on_demand:

need_new_on_demand = self.get_children(element_name) is None

else:

need_new_on_demand = False

if not (child_spec.repeated or need_new_on_demand):

raise ValueError('A <{}> child already exists, please access it directly.'

.format(element_name))

new_element = _make_element(child_spec, self, attributes=kwargs)

if position is not None:

self._children.insert(position, new_element)

else:

self._children.append(new_element)

self.namescope.increment_revision()

return new_element

def __getattr__(self, name):

if self._last_attribute_error:

# This means that we got here through a @property raising AttributeError.

# We therefore just re-raise the last AttributeError back to the user.

# Note that self._last_attribute_error was set by our specially

# instrumented @property decorator.

exc = self._last_attribute_error

self._last_attribute_error = None

raise exc # pylint: disable=raising-bad-type

elif name in self._spec.children:

return self.get_children(name)

elif name in self._spec.attributes:

return self._get_attribute(name)

elif name == constants.DCLASS and constants.CLASS in self._spec.attributes:

return self._get_attribute(constants.CLASS)

else:

raise AttributeError('object has no attribute: {}'.format(name))

def __setattr__(self, name, value):

# If this name corresponds to a descriptor for a slotted attribute or

# settable property then try to invoke the descriptor to set the attribute

# and return if successful.

klass_attr = getattr(type(self), name, None)

if klass_attr is not None:

try:

return klass_attr.__set__(self, value)

except AttributeError:

pass

# If we did not find a settable descriptor then we look in the attribute

# spec to see if there is a MuJoCo attribute matching this name.

attribute_name = name if name != constants.DCLASS else constants.CLASS

if attribute_name in self._spec.attributes:

self._set_attribute(attribute_name, value)

else:

raise AttributeError('can\'t set attribute: {}'.format(name))

def __delattr__(self, name):

if name in self._spec.children:

if self._spec.children[name].repeated:

raise AttributeError(

'`{0}` is a collection of child elements, '

'which cannot be deleted. Did you mean to call `{0}.clear()`?'

.format(name))

else:

return self.get_children(name).remove()

elif name in self._spec.attributes:

return self._remove_attribute(name)

else:

raise AttributeError('object has no attribute: {}'.format(name))

def _check_attachments_on_remove(self, affect_attachments):

if not affect_attachments and self._attachments:

raise ValueError(

'please use remove(affect_attachments=True) as this will affect some '

'attributes and/or children belonging to an attached model')

for child in self._children:

child._check_attachments_on_remove(affect_attachments) # pylint: disable=protected-access

def remove(self, affect_attachments=False):

"""Removes this element from the model."""

self._check_attachments_on_remove(affect_attachments)

if affect_attachments:

for attachment in self._attachments.values():

attachment.remove(affect_attachments=True)

for child in list(self._children):

child.remove(affect_attachments)

if self._spec.repeated or self._spec.on_demand:

self._parent._children.remove(self) # pylint: disable=protected-access

for attribute in self._attributes.values():

attribute._force_clear() # pylint: disable=protected-access

self._parent = None

self._is_removed = True

else:

for attribute in self._attributes.values():

attribute._force_clear() # pylint: disable=protected-access

self.namescope.increment_revision()

@property

def is_removed(self):

return self._is_removed

def all_children(self):

all_children = [child for child in self._children]

for attachment in self._attachments.values():

all_children += [child for child in attachment.all_children()

if child.spec.repeated]

return all_children

def to_xml(self, prefix_root=None, debug_context=None,

*,

precision=constants.XML_DEFAULT_PRECISION,

zero_threshold=0):

"""Generates an etree._Element corresponding to this MJCF element.

Args:

prefix_root: (optional) A `NameScope` object to be treated as root

for the purpose of calculating the prefix.

If `None` then no prefix is included.

debug_context: (optional) A `debugging.DebugContext` object to which

the debugging information associated with the generated XML is written.

This is intended for internal use within PyMJCF; users should never need

manually pass this argument.

precision: (optional) Number of digits to output for floating point

quantities.

zero_threshold: (optional) When outputting XML, floating point quantities

whose absolute value falls below this threshold will be treated as zero.

Returns:

An etree._Element object.

"""

prefix_root = prefix_root or self.namescope

xml_element = etree.Element(self._spec.name)

self._attributes_to_xml(xml_element, prefix_root, debug_context,

precision=precision, zero_threshold=zero_threshold)

self._children_to_xml(xml_element, prefix_root, debug_context,

precision=precision, zero_threshold=zero_threshold)

return xml_element

def _attributes_to_xml(self, xml_element, prefix_root, debug_context=None,

*, precision, zero_threshold):

del debug_context # Unused.

for attribute_name, attribute in self._attributes.items():

attribute_value = attribute.to_xml_string(prefix_root,

precision=precision,

zero_threshold=zero_threshold)

if attribute_name == self._spec.identifier and attribute_value is None:

xml_element.set(attribute_name, self.full_identifier)

elif attribute_value is None:

continue

else:

xml_element.set(attribute_name, attribute_value)

def _children_to_xml(self, xml_element, prefix_root, debug_context=None,

*, precision, zero_threshold):

for child in self.all_children():

child_xml = child.to_xml(prefix_root, debug_context,

precision=precision,

zero_threshold=zero_threshold)

if (child_xml.attrib or len(child_xml) # pylint: disable=g-explicit-length-test

or child.spec.repeated or child.spec.on_demand):

xml_element.append(child_xml)

if debugging.debug_mode() and debug_context:

debug_comment = debug_context.register_element_for_debugging(child)

xml_element.append(debug_comment)

if len(child_xml) > 0: # pylint: disable=g-explicit-length-test

child_xml.insert(0, copy.deepcopy(debug_comment))

def to_xml_string(self, prefix_root=None,

self_only=False, pretty_print=True, debug_context=None,

*,

precision=constants.XML_DEFAULT_PRECISION,

zero_threshold=0):

"""Generates an XML string corresponding to this MJCF element.

Args:

prefix_root: (optional) A `NameScope` object to be treated as root

for the purpose of calculating the prefix.

If `None` then no prefix is included.

self_only: (optional) A boolean, whether to generate an XML corresponding

only to this element without any children.

pretty_print: (optional) A boolean, whether to the XML string should be

properly indented.

debug_context: (optional) A `debugging.DebugContext` object to which

the debugging information associated with the generated XML is written.

This is intended for internal use within PyMJCF; users should never need

manually pass this argument.

precision: (optional) Number of digits to output for floating point

quantities.

zero_threshold: (optional) When outputting XML, floating point quantities

whose absolute value falls below this threshold will be treated as zero.

Returns:

A string.

"""

xml_element = self.to_xml(prefix_root, debug_context,

precision=precision,

zero_threshold=zero_threshold)

if self_only and len(xml_element) > 0: # pylint: disable=g-explicit-length-test

etree.strip_elements(xml_element, '*')

xml_element.text = '...'

if (self_only and self._spec.identifier and

not self._attributes[self._spec.identifier].to_xml_string(

prefix_root, precision=precision, zero_threshold=zero_threshold)):

del xml_element.attrib[self._spec.identifier]

xml_string = util.to_native_string(

etree.tostring(xml_element, pretty_print=pretty_print))

if pretty_print and debug_context:

return debug_context.commit_xml_string(xml_string)

else:

return xml_string

def __str__(self):

return self.to_xml_string(self_only=True, pretty_print=False)

def __repr__(self):

return 'MJCF Element: ' + str(self)

def _check_valid_attachment(self, other):

self_spec = self._spec

if self_spec.name == constants.WORLDBODY:

self_spec = self._spec.children[constants.BODY]

other_spec = other.spec

if other_spec.name == constants.WORLDBODY:

other_spec = other_spec.children[constants.BODY]

if other_spec != self_spec:

raise ValueError(

'The attachment must have the same spec as this element.')

def _attach(self, other, exclude_worldbody=False, dry_run=False):

"""Attaches another element of the same spec to this element.

All children of `other` will be treated as children of this element.

All XML attributes which are defined in `other` but not defined in this

element will be copied over, and any conflicting XML attribute value causes

an error. After the attachment, any XML attribute modified in this element

will also affect `other` and vice versa.

Children of this element which are not a repeated elements will also be

attached by the corresponding children of `other`.

Args:

other: Another Element with the same spec.

exclude_worldbody: (optional) A boolean. If `True`, then don't do anything

if `other` is a worldbody.

dry_run: (optional) A boolean, if `True` only verify that the operation

is valid without actually committing any change.

Raises:

ValueError: If `other` has a different spec, or if there are conflicting

XML attribute values.

"""

self._check_valid_attachment(other)

if exclude_worldbody and other.tag == constants.WORLDBODY:

return

if dry_run:

self._check_conflicting_attributes(other, copying=False)

else:

self._attachments[other.namescope] = other

self._sync_attributes(other, copying=False)

self._attach_children(other, exclude_worldbody, dry_run)

if other.tag != constants.WORLDBODY and not dry_run:

other._alias_attributes_dict(self._attributes) # pylint: disable=protected-access

def _detach(self, other_namescope):

"""Detaches a model with the specified namescope."""

attached_element = self._attachments.get(other_namescope)

if attached_element:

attached_element._restore_attributes_dict() # pylint: disable=protected-access

del self._attachments[other_namescope]

for child in self._children:

child._detach(other_namescope) # pylint: disable=protected-access

def _check_conflicting_attributes(self, other, copying):

for attribute_name, other_attribute in other.get_attributes().items():

if attribute_name == constants.DCLASS:

attribute_name = constants.CLASS

if ((not self._attributes[attribute_name].conflict_allowed)

and self._attributes[attribute_name].value is not None

and other_attribute is not None

and np.asarray(

self._attributes[attribute_name].value != other_attribute).any()):

raise ValueError(

'Conflicting values for attribute `{}`: {} vs {}'

.format(attribute_name,

self._attributes[attribute_name].value,

other_attribute))

def _sync_attributes(self, other, copying):

self._check_conflicting_attributes(other, copying)

for attribute_name, other_attribute in other.get_attributes().items():

if attribute_name == constants.DCLASS:

attribute_name = constants.CLASS

self_attribute = self._attributes[attribute_name]

if other_attribute is not None:

if self_attribute.conflict_behavior in _CONFLICT_BEHAVIOR_FUNC:

if self_attribute.value is not None:

self_attribute.value = (

_CONFLICT_BEHAVIOR_FUNC[self_attribute.conflict_behavior](

self_attribute.value, other_attribute))

else:

self_attribute.value = other_attribute

elif copying or not self_attribute.conflict_allowed:

self_attribute.value = other_attribute

def _attach_children(self, other, exclude_worldbody, dry_run=False):

for other_child in other.all_children():

if not other_child.spec.repeated:

self_child = self.get_children(other_child.spec.name)

self_child._attach(other_child, exclude_worldbody, dry_run) # pylint: disable=protected-access

def resolve_references(self):

for attribute in self._attributes.values():

if isinstance(attribute, attribute_types.Reference):

if attribute.value and isinstance(attribute.value, str):

referred = self.root.find(

attribute.reference_namespace, attribute.value)

if referred:

attribute.value = referred

for child in self.all_children():

child.resolve_references()

def _update_references(self, reference_dict):

for attribute in self._attributes.values():

if isinstance(attribute, attribute_types.Reference):

if attribute.value in reference_dict:

attribute.value = reference_dict[attribute.value]

for child in self.all_children():

child._update_references(reference_dict) # pylint: disable=protected-access

class _AttachableElement(_ElementImpl):

"""Specialized object representing a <site> or <worldbody> element.

This element defines a frame to which another MJCF model can be attached.

"""

__slots__ = []

def attach(self, attachment):

"""Attaches another MJCF model at this site.

An empty <body> will be created as an attachment frame. All children of

`attachment`'s <worldbody> will be treated as children of this frame.

Furthermore, all other elements in `attachment` are merged into the root

of the MJCF model to which this element belongs.

Args:

attachment: An MJCF `RootElement`

Returns:

An `mjcf.Element` corresponding to the attachment frame. A joint can be

added directly to this frame to give degrees of freedom to the attachment.

Raises:

ValueError: If `other` is not a valid attachment to this element.

"""