Scheme (scheme)

Scheme Workflow

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

class orangecanvas.scheme.scheme.Scheme(parent=None, title=None, description=None, env={}, **kwargs)

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.

nodes

list of SchemeNode – A list of all the nodes in the scheme.

links

list of SchemeLink – A list of all links in the scheme.

annotations

list of BaseSchemeAnnotation – A list of all the annotations in the scheme.

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])

Signal emitted when the associated runtime environment changes

nodes

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

links

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

annotations

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

set_title(title)

Set the scheme title text.

title

The title (human readable string) of the scheme.

set_description(description)

Set the scheme description text.

description

Scheme description text.

add_node(node)

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.

new_node(description, title=None, position=None, properties=None)

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 ((x, y) tuple of floats, optional) – Optional position in a 2D space.
• properties (dict, optional) – A dictionary of optional extra properties.

See also

SchemeNode(), Scheme.add_node()

remove_node(node)

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.

add_link(link)

Add a link to the scheme.

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

new_link(source_node, source_channel, sink_node, sink_channel)

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)

Remove a link from the scheme.

Parameters:link (SchemeLink) – Link instance to remove.

check_connect(link)

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

Can raise:

• TypeError if link is not an instance of SchemeLink
• 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)

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

Parameters:link (SchemeLink) –

compatible_channels(link)

Return True if the channels in link have compatible types.

Parameters:link (SchemeLink) –

can_connect(link)

Return True if link can be added to the scheme.

See also

Scheme.check_connect()

upstream_nodes(start_node)

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

Parameters:start_node (SchemeNode) –

downstream_nodes(start_node)

Return a set of all nodes downstream from start_node.

Parameters:start_node (SchemeNode) –

is_ancestor(node, child)

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)

Return a set of all children of node.

parents(node)

Return a set of all parents of node.

input_links(node)

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

output_links(node)

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

propose_links(source_node, sink_node)

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.

add_annotation(annotation)

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

remove_annotation(annotation)

Remove the annotation instance from the scheme.

clear()

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

sync_node_properties()

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

The default implementation does nothing.

save_to(stream, pretty=True, pickle_fallback=False)

Save the scheme as an xml formated file to stream

See also

scheme_to_ows_stream()

load_from(stream)

Load the scheme from xml formated stream.

set_runtime_env(key, value)

Set a runtime environment variable key to value

get_runtime_env(key, default=None)

Return a runtime environment variable for key.

runtime_env()

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 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.