pydrake.common.containers

Provides extensions for containers of Drake-related objects.

class pydrake.common.containers.EqualToDict(*args, **kwargs)

Bases: pydrake.common.containers._DictKeyWrap

Implements a dictionary where keys are compared using type and lhs.EqualTo(rhs).

__init__(*args, **kwargs)

pydrake.common.containers.namedview(name, fields, *, sanitize_field_names=True)

Creates a class that is a named view with given fields. When the class is instantiated, it must be given the object that it will be a proxy for. Similar to namedtuple.

If sanitize_field_names is True (the default), then any characters in fields which are not valid in Python identifiers will be automatically replaced with _. Leading numbers will have _ inserted, and duplicate _ will be replaced by a single _.

Example

MyView = namedview("MyView", ('a', 'b'))

value = np.array([1, 2])
view = MyView(value)
view.a = 10  # `value` is now [10, 2]
value[1] = 100  # `view` is now [10, 100]
view[:] = 3  # `value` is now [3, 3]

# Get an array from the view *aliasing* the original vector.
value_view = view[:]
# Another way to get an aliased array.
value_view_2 = np.asarray(view)
# Get an array from the view that is a *copy* of the original
# vector.
value_copy = np.array(view)

Warning

As illustrated above, if you use np.array(view), then it will provide a copied array from the view. If you want an aliased array from the view, then use operations like view[:], np.asarray(view), or np.array(view, copy=False).

For more details, see NamedViewBase.

class pydrake.common.containers.NamedViewBase(value)

Bases: object

Base for classes generated by namedview.

Inspired by: https://gitlab.com/ericvsmith/namedlist

__init__(value)

Creates a view on value. Any mutations on this instance will be reflected in value, and any mutations on value will be reflected in this instance.

classmethod get_fields()

Returns all fields for this class or object.

classmethod Zero()

Constructs a view onto values set to all zeros.