A minimal example to show the usage of dearpygui to construct an nodes app.

dearpygui_nodes.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
This is a minimal example to show the usage of dearpygui
to construct an app of nodes manipulations.
The basic functions includ:
 * drag a button to create a node
 * change node theme
 * show some message based on the selected node
 * connect and disconnect nodes
"""

import dearpygui.dearpygui as dpg

dpg.create_context()
dpg.configure_app(docking=True)

# some global variables
layer_data = {} # list of available layers
connection_data = [] # list of connections from layer to layer
LinkList = []
current_layer = []
selected_nodes = set()
nodes = []


def show_layer_info(sender):
    for selected_node in dpg.get_selected_nodes("NodeEditor"):
        item_name = "Layer Attributes_" + str(selected_node)
        if (selected_node not in nodes):   
            dpg.hide_item(item_name)
        else:
            dpg.show_item(item_name)


# Delete selected node
def callback_delete_item(sender):
    for selected_node in dpg.get_selected_nodes("NodeEditor"):
        # Deleting node and attached links
        ## Extract all children of the deleted node
        selected_node_children = dpg.get_item_children(selected_node)[1]
        ## Extract all existing links in the Node Editor
        nodeEditor_links = dpg.get_item_children("NodeEditor")[0]
        ## Iterate through NodeEditor elements and delete attached links
        for link in nodeEditor_links:
            if dpg.get_item_configuration(link)["attr_1"] in selected_node_children or dpg.get_item_configuration(link)["attr_2"] in selected_node_children:
                dpg.delete_item(link)
        ## Iterate trough LinkList and remove attached links
        for item in LinkList:
            for sub_item in item:
                if dpg.get_item_alias(selected_node) in sub_item:
                    LinkList.remove(item) 
        # Deleting node
        dpg.delete_item(selected_node)
        del model_data[selected_node]


# callback runs when user attempts to connect attributes
def link_callback(sender, app_data):
    # app_data -> (link_id1, link_id2)
    data = ()

    if type(app_data) == tuple:
        dpg.add_node_link(app_data[0], app_data[1], parent=sender)
        data = (dpg.get_item_alias(app_data[0]), dpg.get_item_alias(app_data[1]))

        LinkList.append(data)
    

# callback runs when user attempts to disconnect attributes
def delink_callback(sender, app_data):
    # app_data -> link_id
    dpg.delete_item(app_data)


def input_callback(sender, app_data):
    # get parent node
    parent = dpg.get_item_parent(sender)
    parent = dpg.get_item_parent(parent)
    label = dpg.get_item_label(sender)
    print("input callback: ", app_data, "parent: ", parent, "label: ", label)
    model_data[parent]["parameters"][0]["value"] = dpg.get_value(sender)
    print(model_data)


def on_drop(sender, app_data, user_data):

    pos = dpg.get_mouse_pos(local=False)

    layer_info = app_data

    node_id = dpg.generate_uuid()

    nodes.append(node_id)

    with dpg.node(label="node_"+str(node_id), tag=node_id, parent="NodeEditor", pos=pos):

        with dpg.node_attribute():
            dpg.add_input_int(label="input", callback=input_callback, width=100)

        with dpg.node_attribute(attribute_type=dpg.mvNode_Attr_Output):
            dpg.add_input_int(label="output", callback=input_callback, width=100)

    # create group for display on window "layer_info"

    group_lable = "Layer Attributes_" + str(node_id)
    with dpg.group(label=group_lable, tag=group_lable, parent="window_info", show=False):  
        dpg.add_text("some info")
        dpg.add_text("some more info")

# get selected nodes when dragging mouse
def on_drag(sender, app_data):
    selected_nodes.clear()
    for selected_node in dpg.get_selected_nodes("NodeEditor"):
        selected_nodes.add(selected_node)

# 
def get_selected_nodes_callback(sender, app_data):
    if len(selected_nodes) == 0:
        selected_nodes.clear()
        return
    print("selected nodes: ", selected_nodes)


with dpg.theme() as item_theme:
    with dpg.theme_component(dpg.mvNode):
        link_theme_color = dpg.add_theme_color(dpg.mvNodeCol_TitleBar, (0, 255, 0), category=dpg.mvThemeCat_Nodes)

# create window context
with dpg.window(label="Tutorial", width=1200, height=800):

    # create node editor
    with dpg.group(tag="nodes", drop_callback=on_drop, user_data="test"):
        
        with dpg.node_editor(tag="NodeEditor", callback=link_callback, delink_callback=delink_callback):
            with dpg.node(label="Input") as node_test:
                with dpg.node_attribute(label="Node A1", attribute_type=dpg.mvNode_Attr_Static):
                    #dpg.add_input_float(label="F1", width=150)
                    pass

                with dpg.node_attribute(label="Node A2", attribute_type=dpg.mvNode_Attr_Output):
                    dpg.add_input_int(label="F1", width=100)
                    dpg.add_input_int(label="F2", width=100)

            dpg.bind_item_theme(node_test, item_theme)

    # create button window
    with dpg.window(label="buttons", pos=(200, 100)):

        def add_button(name):
            dpg.add_button(label=name, tag=name)
            with dpg.drag_payload(parent=name):
                dpg.add_text(name)
                
        with dpg.group(tag="buttons"):
            for i in range(5):
                add_button(f"button{i}")
                dpg.add_separator()


    # window to show layer properties
    with dpg.window(label="Info Window", tag="window_info", pos=(400, 100)):
        dpg.add_text("Information", show=True)
        dpg.add_separator(show=True)


    # create menubar
    with dpg.viewport_menu_bar():
        with dpg.menu(label="File"):
            dpg.add_menu_item(label="save")


    # input handlers
    with dpg.handler_registry():
        dpg.add_key_release_handler(key=dpg.mvKey_Delete, callback=callback_delete_item)
        dpg.add_mouse_click_handler(callback=show_layer_info)
        dpg.add_mouse_drag_handler(callback=on_drag)
        dpg.add_mouse_release_handler(callback=get_selected_nodes_callback)


dpg.create_viewport(title='Custom Title', width=1200, height=800)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()