Pyodide Canvas

Artifacts

Important: Pyodide takes time to initialize. Initialization completion is indicated by a red border around Run all button.

System Imports

These are available from Pyodide, but you may wish to make sure that they are installed if you are attempting to run the program directly on the machine.

matplotlib
networkx

others

Available Packages

These are packages that refer either to my previous posts or to pure python packages that I have compiled, and is available in the below locations. As before, install them if you need to run the program directly on the machine.

define the picture

draw

derivation tree

program

from graphviz import Digraph

import re
def dot_escape(s):
    """Return s in a form suitable for dot"""
    s = re.sub(r'([^a-zA-Z0-9" ])', r"\\\1", s)
    return s

def extract_node(node, id):
    symbol, children, *annotation = node
    return symbol, children, ''.join(str(a) for a in annotation)

def default_node_attr(dot, nid, symbol, ann):
    dot.node(repr(nid), dot_escape(symbol))

def default_edge_attr(dot, start_node, stop_node):
    dot.edge(repr(start_node), repr(stop_node))
def default_graph_attr(dot):
    dot.attr('node', shape='plain')
def display_tree(derivation_tree,
                 log=False,
                 extract_node=extract_node,
                 node_attr=default_node_attr,
                 edge_attr=default_edge_attr,
                 graph_attr=default_graph_attr):

# If we import display_tree, we also have to import its functions
    from graphviz import Digraph

counter = 0
    labels = {}

def traverse_tree(dot, tree, id=0):
        (symbol, children, annotation) = extract_node(tree, id)
        labels[str(id)] = symbol
        node_attr(dot, id, symbol, annotation)

if children:
            for child in children:
                nonlocal counter
                counter += 1
                child_id = counter
                edge_attr(dot, id, child_id)
                traverse_tree(dot, child, child_id)

dot = Digraph(comment="Derivation Tree")
    graph_attr(dot)
    traverse_tree(dot, derivation_tree)
    if log:
        print(dot)
    return dot, labels

display

pydot

Artifacts

The runnable Python source for this notebook is available here.

Contents

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