Scheme (scheme)

Scheme Workflow

The Scheme class defines a DAG (Directed Acyclic Graph) workflow.

class orangecanvas.scheme.scheme.Scheme(parent: Optional[PyQt5.QtCore.QObject] = None, title: str = '', description: str = '', env: Mapping[str, Any] = {}, **kwargs: Any)

Bases: PyQt5.QtCore.QObject

An QObject subclass representing the scheme widget workflow with annotations.

Parameters

• parent (QObject) – A parent QObject item (default None).

• title (str) – The scheme title.

• description (str) – A longer description of the scheme.

• env (Mapping[str, Any]) – Extra workflow environment definition (application defined).

title_changed(title)

Signal emitted when the title of scheme changes.

description_changed(description)

Signal emitted when the description of scheme changes.

node_added(node)

Signal emitted when a node is added to the scheme.

node_removed(node)

Signal emitted when a node is removed from the scheme.

link_added(link)

Signal emitted when a link is added to the scheme.

link_removed(link)

Signal emitted when a link is removed from the scheme.

annotation_added(annotation)

Signal emitted when a annotation is added to the scheme.

annotation_removed(annotation)

Signal emitted when a annotation is removed from the scheme.

runtime_env_changed(key: str, newvalue: Optional[str], oldvalue: Optional[str])

property nodes

A list of all nodes (SchemeNode) currently in the scheme.

property links

A list of all links (SchemeLink) currently in the scheme.

property annotations

A list of all annotations (BaseSchemeAnnotation) in the scheme.

set_title(title: str) → None

Set the scheme title text.

title: str

The title (human readable string) of the scheme.

set_description(description: str) → None

Set the scheme description text.

description: str

Scheme description text.

add_node(node: orangecanvas.scheme.node.SchemeNode) → None

Add a node to the scheme. An error is raised if the node is already in the scheme.

Parameters

node (SchemeNode) – Node instance to add to the scheme.

insert_node(index: int, node: orangecanvas.scheme.node.SchemeNode)

Insert node into self.nodes at the specified position index

new_node(description: orangecanvas.registry.description.WidgetDescription, title: Optional[str] = None, position: Optional[Tuple[float, float]] = None, properties: Optional[dict] = None) → orangecanvas.scheme.node.SchemeNode

Create a new SchemeNode and add it to the scheme.

Same as:

scheme.add_node(SchemeNode(description, title, position,
                           properties))

Parameters

• description (WidgetDescription) – The new node’s description.

• title (str, optional) – Optional new nodes title. By default description.name is used.

• position (Tuple[float, float]) – Optional position in a 2D space.

• properties (dict, optional) – A dictionary of optional extra properties.

See also

SchemeNode, Scheme.add_node

remove_node(node: orangecanvas.scheme.node.SchemeNode) → orangecanvas.scheme.node.SchemeNode

Remove a node from the scheme. All links into and out of the node are also removed. If the node in not in the scheme an error is raised.

Parameters

node (SchemeNode) – Node instance to remove.

insert_link(index: int, link: orangecanvas.scheme.link.SchemeLink)

Insert link into self.links at the specified position index.

add_link(link: orangecanvas.scheme.link.SchemeLink) → None

Add a link to the scheme.

Parameters

link (SchemeLink) – An initialized link instance to add to the scheme.

new_link(source_node: orangecanvas.scheme.node.SchemeNode, source_channel: orangecanvas.registry.description.OutputSignal, sink_node: orangecanvas.scheme.node.SchemeNode, sink_channel: orangecanvas.registry.description.InputSignal) → orangecanvas.scheme.link.SchemeLink

Create a new SchemeLink from arguments and add it to the scheme. The new link is returned.

Parameters

• source_node (SchemeNode) – Source node of the new link.

• source_channel (OutputSignal) – Source channel of the new node. The instance must be from source_node.output_channels()

• sink_node (SchemeNode) – Sink node of the new link.

• sink_channel (InputSignal) – Sink channel of the new node. The instance must be from sink_node.input_channels()

See also

SchemeLink, Scheme.add_link

remove_link(link: orangecanvas.scheme.link.SchemeLink) → None

Remove a link from the scheme.

Parameters

link (SchemeLink) – Link instance to remove.

check_connect(link: orangecanvas.scheme.link.SchemeLink) → None

Check if the link can be added to the scheme and raise an appropriate exception.

Can raise:

• SchemeCycleError if the link would introduce a loop in the graph which does not allow loops.

• IncompatibleChannelTypeError if the channel types are not compatible

• SinkChannelError if a sink channel has a Single flag specification and the channel is already connected.

• DuplicatedLinkError if a link duplicates an already present link.

creates_cycle(link: orangecanvas.scheme.link.SchemeLink) → bool

Return True if link would introduce a cycle in the scheme.

Parameters

link (SchemeLink) –

compatible_channels(link: orangecanvas.scheme.link.SchemeLink) → bool

Return True if the channels in link have compatible types.

Parameters

link (SchemeLink) –

can_connect(link: orangecanvas.scheme.link.SchemeLink) → bool

Return True if link can be added to the scheme.

See also

Scheme.check_connect

upstream_nodes(start_node: orangecanvas.scheme.node.SchemeNode) → Set[orangecanvas.scheme.node.SchemeNode]

Return a set of all nodes upstream from start_node (i.e. all ancestor nodes).

Parameters

start_node (SchemeNode) –

downstream_nodes(start_node: orangecanvas.scheme.node.SchemeNode) → Set[orangecanvas.scheme.node.SchemeNode]

Return a set of all nodes downstream from start_node.

Parameters

start_node (SchemeNode) –

is_ancestor(node: orangecanvas.scheme.node.SchemeNode, child: orangecanvas.scheme.node.SchemeNode) → bool

Return True if node is an ancestor node of child (is upstream of the child in the workflow). Both nodes must be in the scheme.

Parameters

• node (SchemeNode) –

• child (SchemeNode) –

children(node: orangecanvas.scheme.node.SchemeNode) → Set[orangecanvas.scheme.node.SchemeNode]

Return a set of all children of node.

parents(node: orangecanvas.scheme.node.SchemeNode) → Set[orangecanvas.scheme.node.SchemeNode]

Return a set of all parents of node.

input_links(node: orangecanvas.scheme.node.SchemeNode) → List[orangecanvas.scheme.link.SchemeLink]

Return a list of all input links (SchemeLink) connected to the node instance.

output_links(node: orangecanvas.scheme.node.SchemeNode) → List[orangecanvas.scheme.link.SchemeLink]

Return a list of all output links (SchemeLink) connected to the node instance.

propose_links(source_node: orangecanvas.scheme.node.SchemeNode, sink_node: orangecanvas.scheme.node.SchemeNode, source_signal: Optional[orangecanvas.registry.description.OutputSignal] = None, sink_signal: Optional[orangecanvas.registry.description.InputSignal] = None) → List[Tuple[orangecanvas.registry.description.OutputSignal, orangecanvas.registry.description.InputSignal, int]]

Return a list of ordered (OutputSignal, InputSignal, weight) tuples that could be added to the scheme between source_node and sink_node.

Note

This can depend on the links already in the scheme.

insert_annotation(index: int, annotation: orangecanvas.scheme.annotations.BaseSchemeAnnotation) → None

Insert annotation into self.annotations at the specified position index.

add_annotation(annotation: orangecanvas.scheme.annotations.BaseSchemeAnnotation) → None

Add an annotation (BaseSchemeAnnotation subclass) instance to the scheme.

remove_annotation(annotation: orangecanvas.scheme.annotations.BaseSchemeAnnotation) → None

Remove the annotation instance from the scheme.

clear() → None

Remove all nodes, links, and annotation items from the scheme.

sync_node_properties() → None

Called before saving, allowing a subclass to update/sync.

The default implementation does nothing.

save_to(stream, pretty=True, **kwargs)

Save the scheme as an xml formatted file to stream

See also

readwrite.scheme_to_ows_stream

load_from(stream, *args, **kwargs)

Load the scheme from xml formatted stream.

Any extra arguments are passed to readwrite.scheme_load

See also

readwrite.scheme_load

set_runtime_env(key: str, value: Any) → None

Set a runtime environment variable key to value

get_runtime_env(key: str, default: Optional[Any] = None) → Any

Return a runtime environment variable for key.

runtime_env() → Mapping[str, Any]

Return (a view to) the full runtime environment.

The return value is a types.MappingProxyType of the underlying environment dictionary. Changes to the env. will be reflected in it.

class WindowGroup(name='', default=False, state=[])

Bases: types.SimpleNamespace

window_group_presets() → List[WindowGroup]

Return a collection of preset window groups and their encoded states.

The base implementation returns an empty list.

class orangecanvas.scheme.scheme.SchemeCycleError

Bases: orangecanvas.scheme.errors.SchemeTopologyError

A link would create a cycle in the scheme.

class orangecanvas.scheme.scheme.IncompatibleChannelTypeError

Bases: TypeError

Source and sink channels do not have compatible types

class orangecanvas.scheme.scheme.SinkChannelError

Bases: orangecanvas.scheme.errors.SchemeTopologyError

Sink channel already connected.

class orangecanvas.scheme.scheme.DuplicatedLinkError

Bases: orangecanvas.scheme.errors.SchemeTopologyError

A link duplicates another link already present in the scheme.