Pythonで単純な四則演算の構文ツリーの可視化を実現する方法

{
	"name": "A",
	"children": [
		"name": "B",
		"children": []
	]
}

"""
Python's AST
利用 Python 的 ast 模块来解析表达式（简单的二元运算），
然后通过遍历语法树来生成 JSON 表示，再使用 PYthon 的库来
将其可视化。这个程序的目的是为了验证自己写的简易解析器是否正确。
"""

import ast
import json


# 操作类型和操作符映射的字典
OPERATORS = {
    ast.Add: "+",
    ast.Sub: "-",
    ast.Mult: "*",
    ast.Div: "/"
}


def generate(tree: ast.Module):
    """
    generate expression AST's representation of JSON
    """
    if not tree:
        raise Exception("Emtpy AST tree!")
    if tree.__class__ == ast.Module:
        print(json.dumps({
            "name": "Expr",
            "children": [DFS(tree.body[0].value)]  # type: ignore
        }, indent=4))


def DFS(node):
    """
    DFS AST
    """
    if not node:
        return {}

    if node.__class__ == ast.BinOp:
        return {
            "name": "BinOp",
            "children": [
                {
                    "name": "left",
                    "children": [
                        DFS(node.left)
                    ]
                },
                DFS(node.op),
                {
                    "name": "left",
                    "children": [
                        DFS(node.right)
                    ]
                }
            ]
        }

    if node.__class__ == ast.Constant:
        return {
            "name": "NUMBER",
            "children": [
                {
                    "name": str(node.value)  # Python 的绘图库，必须是字符串才能正常显示
                }
            ]
        }

    if node.__class__ in [ast.Add, ast.Sub, ast.Mult, ast.Div]:
        return {
            "name": "Op",
            "children": [
                {
                    "name": OPERATORS[node.__class__]
                }
            ]
        }

    # 这里我只处理 加减乘除和数字类型的运行
    raise Exception("There is not support extra type.")


if __name__ == "__main__":
    ast_tree = ast.parse("1+2+3+4+5")
    print(ast.dump(ast_tree, indent=4))
    generate(ast_tree)

"""
Python's AST
利用 Python 的 ast 模块来解析表达式（简单的二元运算），
然后通过遍历语法树来生成 JSON 表示，再使用 PYthon 的库来
将其可视化。这个程序的目的是为了验证自己写的简易解析器是否正确。
"""

import ast
import json


# 操作类型和操作符映射的字典
OPERATORS = {
    ast.Add: "+",
    ast.Sub: "-",
    ast.Mult: "*",
    ast.Div: "/"
}

class JSONVisitor(ast.NodeVisitor):
    """
    JSON visitor: Traversal AST and generate JSON representation
    """

    def visit_Module(self, node):
        module = {
            "name": "Module",
            "children": []
        }
        for sub_node in node.body:
            module["children"].append(self.visit(sub_node))

        return module

    def visit_Expr(self, node):
        return {
            "name": "Expr",
            "children": [
                self.visit(node.value)
            ]
        }

    def visit_BinOp(self, node):
        return {
            "name": "BinOp",
            "children": [
                {
                    "name": "left",
                    "children": [
                        self.visit(node.left)
                    ]
                },
                self.visit(node.op),
                {
                    "name": "right",
                    "children": [
                        self.visit(node.right)
                    ]
                }
            ]
        }

    def visit_Constant(self, node):
        return {
            "name": "NUMBER",
            "children": [{
                "name": str(node.value)  # # Python 的绘图库，必须是字符串才能正常显示
            }]
        }

    def visit_Add(self, node):
        return self.__visit(node)

    def visit_Sub(self, node):
        return self.__visit(node)

    def visit_Mult(self, node):
        return self.__visit(node)

    def visit_Div(self, node):
        return self.__visit(node)

    def __visit(self, node):
        return {
            "name": "Op",
            "children": [{
                "name": OPERATORS[node.__class__]
            }]
        }


if __name__ == "__main__":
    ast_tree = ast.parse("1+2+3+4+5")
    visitor = JSONVisitor()
    json_str = visitor.visit(ast_tree)
    print(json.dumps(json_str, indent=4))