Use when automating Sverchok from Python -- creating node trees programmatically, connecting sockets, setting parameters, or running batch parametric studies. Prevents the common mistake of not calling process_from_nodes() after modifying parameters (tree won't update). Covers node creation, socket connections, parameter sweeps, and batch processing. Keywords: Sverchok API, programmatic, node creation, socket connection, batch processing, parameter sweep, process_from_nodes, automation, Python scripting, create nodes from code, automate Sverchok.
license
MIT
compatibility
Designed for Claude Code. Requires Blender 4.0+/5.x with Sverchok v1.4.0+.
metadata
{"author":"OpenAEC-Foundation","version":"1.0"}
sverchok-syntax-api
Quick Reference
What This Skill Covers
Programmatic (external) control of Sverchok node trees via Python scripts — creating, modifying, querying, and batch-processing node trees from outside the node editor. This skill covers the external API surface for automating Sverchok.
Tree access: bpy.data.node_groups filtered by bl_idname='SverchCustomTreeType'
Node creation: with location and property assignment
tree.nodes.new(bl_idname)
Link creation: tree.links.new(output_socket, input_socket)
Data extraction: node.outputs[name].sv_get() for reading computed results
Batch processing: Parameter sweeps with setattr() + force_update() loops
Performance: tree.init_tree() context manager for suppressing intermediate updates
Data utilities: match_long_repeat, fullList, repeat_last from sverchok.data_structure
Cross-reference: This skill builds on bpy.data knowledge covered by the blender-core-api skill. See that skill for general Blender data-block access patterns.
Critical Warnings
NEVER add nodes or links without tree.init_tree() context manager — every tree.nodes.new() and tree.links.new() call triggers a full tree re-evaluation without it, causing O(n²) performance.
NEVER call node.process() directly — ALWAYS use tree.force_update() or tree.update_nodes() to trigger evaluation through the update system.
NEVER mutate data returned by sv_get(deepcopy=False) — this corrupts the upstream node's cached output and poisons all downstream nodes.
NEVER forget to call tree.force_update() after programmatic property changes — setattr() on node properties does NOT automatically trigger the update system.
ALWAYS set tree.sv_process = True before expecting tree updates — trees with processing disabled silently ignore all events.
ALWAYS use 'SverchCustomTreeType' as the tree type — using 'ShaderNodeTree' or other Blender tree types will fail to create Sverchok nodes.
ALWAYS wrap socket data in nested lists — sv_set([[(0,0,0), (1,0,0)]]) not sv_set([(0,0,0), (1,0,0)]).
Decision Tree
Need to automate Sverchok from Python?
├── Create a new node tree
│ ├── tree = bpy.data.node_groups.new(name, 'SverchCustomTreeType')
│ └── ALWAYS wrap construction in: with tree.init_tree():
├── Access an existing tree
│ ├── tree = bpy.data.node_groups.get('TreeName')
│ └── Verify: tree.bl_idname == 'SverchCustomTreeType'
├── Add nodes to a tree
│ ├── node = tree.nodes.new('SvBoxNodeMk2')
│ ├── Set location: node.location = (x, y)
│ └── Set properties: node.property_name = value
├── Connect nodes
│ ├── By index: tree.links.new(node_a.outputs[0], node_b.inputs[0])
│ └── By name: tree.links.new(node_a.outputs['Vertices'], node_b.inputs['vertices'])
├── Trigger evaluation
│ ├── Full tree: tree.force_update()
│ ├── Specific nodes: tree.update_nodes([node_a, node_b])
│ └── First ensure: tree.sv_process = True
├── Read output data
│ ├── data = node.outputs['Name'].sv_get()
│ ├── Read-only: sv_get(deepcopy=False)
│ └── Data is ALWAYS nested: [[obj1_data], [obj2_data], ...]
└── Batch parameter sweep
├── Loop: setattr(node, prop, value) → tree.force_update() → sv_get()
└── Disable viewers for speed: tree.sv_show = False
Essential Patterns
Pattern 1: Create a New Node Tree
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
# Create a new Sverchok tree (uses bpy.data: see blender-core-api skill)
tree = bpy.data.node_groups.new("MyParametricTree", 'SverchCustomTreeType')
# ALWAYS use init_tree() to suppress updates during constructionwith tree.init_tree():
# Add nodes by bl_idname
num = tree.nodes.new('SvNumberNode')
num.location = (0, 0)
box = tree.nodes.new('SvBoxNodeMk2')
box.location = (200, 0)
viewer = tree.nodes.new('SvViewerDrawMk4')
viewer.location = (400, 0)
# Create links: output socket → input socket
tree.links.new(num.outputs[0], box.inputs['Size'])
tree.links.new(box.outputs['Vertices'], viewer.inputs['vertices'])
tree.links.new(box.outputs['Edges'], viewer.inputs['edges'])
tree.links.new(box.outputs['Faces'], viewer.inputs['faces'])
# Force initial evaluation after construction
tree.force_update()
Pattern 2: Access and Query Existing Trees
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
# List all Sverchok trees (bpy.data.node_groups: see blender-core-api skill)
sv_trees = [
ng for ng in bpy.data.node_groups
if ng.bl_idname == 'SverchCustomTreeType'
]
# Access a specific tree with validation
tree = bpy.data.node_groups.get("MyTree")
if tree isNoneor tree.bl_idname != 'SverchCustomTreeType':
raise RuntimeError("Sverchok tree 'MyTree' not found")
# Query tree stateprint(f"Processing: {tree.sv_process}")
print(f"Animation: {tree.sv_animate}")
print(f"Draft: {tree.sv_draft}")
print(f"Nodes: {len(tree.nodes)}, Links: {len(tree.links)}")
Pattern 3: Read Node Output Data
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
tree = bpy.data.node_groups["MyTree"]
tree.sv_process = True
tree.force_update()
node = tree.nodes["Box"]
# sv_get() returns nested lists: [[object1_data], [object2_data], ...]try:
vertices = node.outputs['Vertices'].sv_get(deepcopy=False) # Read-onlyfor obj_idx, verts inenumerate(vertices):
print(f"Object {obj_idx}: {len(verts)} vertices")
except Exception:
print("No data — node may not have been processed")
# ALWAYS use deepcopy=True (default) if you will modify the data
vertices = node.outputs['Vertices'].sv_get() # deepcopy=True is default
Pattern 4: Modify Node Properties
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
tree = bpy.data.node_groups["MyTree"]
tree.sv_process = True# Set node properties via setattr or direct assignment
node = tree.nodes["Formula"]
node.formula1 = "sin(x) * R"# Set properties on SNLite script nodes
snlite = tree.nodes["Scripted Node Lite"]
snlite.script_name = "my_script.py"# ALWAYS force update after programmatic property changes
tree.force_update()
Pattern 5: Batch Parameter Sweep
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
defbatch_sweep(tree_name, param_sets):
"""Run a parameter sweep across a Sverchok tree.
Args:
tree_name: Name of the Sverchok node tree
param_sets: list of [(node_name, prop_name, value), ...]
Returns:
list of extracted output data per parameter set
"""
tree = bpy.data.node_groups[tree_name]
tree.sv_process = True
tree.sv_show = False# Disable viewport display for speed
results = []
for params in param_sets:
# Apply all parameter valuesfor node_name, prop_name, value in params:
setattr(tree.nodes[node_name], prop_name, value)
# Force full recalculation
tree.force_update()
# Extract results
output_node = tree.nodes["Output"]
data = output_node.outputs[0].sv_get(deepcopy=False)
results.append(data)
tree.sv_show = True# Re-enable viewport displayreturn results
# Usage:# results = batch_sweep("MyTree", [# [("NumberNode", "int_", 5), ("ScaleNode", "factor", 2.0)],# [("NumberNode", "int_", 10), ("ScaleNode", "factor", 3.0)],# ])
Pattern 6: Trigger Updates Correctly
# Blender 4.0+/5.x with Sverchok v1.4.0+import bpy
tree = bpy.data.node_groups["MyTree"]
# ALWAYS ensure processing is enabled first
tree.sv_process = True# Full tree recalculation (ForceEvent)
tree.force_update()
# Update specific nodes and their downstream dependents only
tree.update_nodes([tree.nodes["NodeA"], tree.nodes["NodeB"]])
# Enable animation updates (tree reacts to frame changes)
tree.sv_animate = True# Enable scene change updates
tree.sv_scene_update = True
Pattern 7: Data Matching Utilities
# Sverchok v1.4.0+from sverchok.data_structure import match_long_repeat, fullList, repeat_last
# match_long_repeat: extend shorter lists by repeating last element
verts = [[(0,0,0), (1,0,0)], [(2,0,0), (3,0,0), (4,0,0)]]
scales = [[2.0]] # 1 object, but 2 objects of verts
matched = match_long_repeat([verts, scales])
# scales becomes [[2.0], [2.0]]: repeated to match 2 objects# fullList: in-place extend a list to minimum length
my_list = [1.0, 2.0]
fullList(my_list, 5)
# my_list is now [1.0, 2.0, 2.0, 2.0, 2.0]# repeat_last: infinite iterator that repeats the last element
gen = repeat_last([10, 20, 30])
values = [next(gen) for _ inrange(6)]
# values: [10, 20, 30, 30, 30, 30]
Common Operations
Tree Properties
Property
Type
Default
Description
tree.sv_process
BoolProperty
True
Enable/disable tree processing
tree.sv_animate
BoolProperty
False
Process on frame change
tree.sv_show
BoolProperty
True
Show viewer outputs in viewport
tree.sv_draft
BoolProperty
False
Draft mode (reduced quality for speed)
tree.sv_scene_update
BoolProperty
False
React to scene changes
Tree Methods
Method
Description
tree.force_update()
Force complete tree recalculation (ForceEvent)
tree.update_nodes(nodes)
Update specific nodes and downstream dependents
tree.init_tree()
Context manager — suppresses updates during construction
Socket Data Methods
Method
Description
socket.sv_get(default=None, deepcopy=True)
Read data from socket cache
socket.sv_set(data)
Write data to socket cache
socket.sv_forget()
Clear cached data
Key Data Structure Functions
Function
Import
Description
updateNode
sverchok.data_structure
Property update callback for bpy.props
match_long_repeat(lists)
sverchok.data_structure
Match list lengths by repeating last element
fullList(lst, count)
sverchok.data_structure
Extend list in-place to target length
repeat_last(lst)
sverchok.data_structure
Infinite iterator repeating last element
flat_iter(data)
sverchok.data_structure
Deep flatten nested structures
get_data_nesting_level(data)
sverchok.data_structure
Determine nesting depth
List Matching Modes
Mode
Function
Behavior
"SHORT"
match_short
Truncate to shortest list
"CYCLE"
match_long_cycle
Cycle shorter lists
"REPEAT"
match_long_repeat
Repeat last element of shorter lists
"XREF"
match_cross
Cross-reference (all combinations)
Access via: from sverchok.data_structure import list_match_func
