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Examples

Quick Demo

Run It

cd examples/flet_nodes_example
uv run --active flet -r src/main.py

What You'll See

  1. Register Types button → loads example node logic
  2. Demo Nodes button → creates nodes on the canvas
  3. A node editor with draggable nodes and connectable ports
  4. Execute Selected button → runs the graph

What the Example Includes

Node Type What It Does
Value A, Value B Input nodes with text fields
Add Adds two numbers
Multiply Multiplies two numbers
Print Outputs to console
If/Else Conditional branching

Common Patterns

1. Input Node with UI Fallback

class InputLogic(BaseNodeLogic):
    async def execute(self, node, **inputs):
        # Use UI textfield if no connected input
        if node.ui_content and hasattr(node.ui_content, 'value'):
            return {'value': node.ui_content.value}
        return {'value': inputs.get('default', '')}

2. Processing Pipeline

[Input A] ──→ [Add] ──→ [Multiply] ──→ [Print]
[Input B] ──→ [  +  ]

Connect ports to wire data through the pipeline, then execute the final node.

3. Conditional Logic

class IfElseLogic(BaseNodeLogic):
    async def execute(self, node, **inputs):
        condition = bool(inputs.get('condition', False))
        if condition:
            return {'result': inputs.get('true_val', None)}
        else:
            return {'result': inputs.get('false_val', None)}

4. Node with Side Effects

class SaveToFileLogic(BaseNodeLogic):
    async def execute(self, node, **inputs):
        data = inputs.get('data', '')
        filepath = inputs.get('path', 'output.txt')

        with open(filepath, 'w') as f:
            f.write(str(data))

        return {'status': 'saved'}

Tips for Building Graphs

  • Start simple: Create a few nodes, connect them, execute to see flow
  • Debug with Print: Insert PrintLogic nodes to inspect intermediate values
  • Check types: Ensure output types match input expectations
  • Avoid cycles: The engine detects them, but graphs won't execute
  • Test independently: Unit-test logic classes before using them in graphs

Example Files

  • examples/flet_nodes_example/src/main.py — Demo UI app
  • src/flet_nodes/example_logic.py — Logic implementations (Add, Multiply, Print, etc.)
  • test_execution_engine.py — Unit test examples