用Python实现一个Lisp解析器

一、模块代码

Talk is cheap, show the code:

# lisp.pyimport rescanner = re.Scanner([(r'\s+', None),(r'[^"()\s]+|"[^"]*"', lambda scanner, token: ('NAME', token)),(r'\(', lambda scanner, token: (token, token)),(r'\)', lambda scanner, token: (token, token)),
])class Node:def __init__(self, parent=None, name=None):self.parent = parentself.name = name if parent else 'root'self.children = []if parent:parent.children.append(self)@propertydef stripname(self):return self.name.strip('"')def __add__(self, item):assert isinstance(item, str), type(item)if self.name is None:self.name = itemelse:Node(self, item)return selfdef __contains__(self, item):return any(item == node for level, node in self)def __eq__(self, item):assert isinstance(item, str), type(item)return item == self.namedef __getitem__(self, item):assert isinstance(item, (int, str)), type(item)if isinstance(item, int):return self.children[item]if isinstance(item, str):return (node for level, node in self if node == item)def __iter__(self, level=0):yield level, selffor child in self.children:yield from child.__iter__(level + 1)def __repr__(self):return f'Node({self.name!r})'def __str__(self):lines = [level * '| ' + node.name for level, node in self]return '\n'.join(lines)def ParseLisp(text):results, remainder = scanner.scan(text)assert remainder == '', repr(remainder[:200])types = [typ for typ, name in results]assert types.count('NEXT') == types.count('PREV'), (types.count('NEXT'), types.count('PREV'))root = node = Node()for typ, name in results:if typ == '(':node = Node(node)elif typ == ')':node = node.parentelif typ == 'NAME':node += namereturn root

二、用法参考

import lisptext = '''(status(written(timestamp 2022 3 17 10 33 1)(author "Mentor Graphics Corporation")(program "xDX Designer Edif Exporter"(version "X-ENTP VX.2.8 <17297288>  2020-10-02 15:37:39"))))(status(written(timestamp 2024 6 1 6 3 19)(author "Shixian Li")(program "Lisp Parser"(version "v1.0.2  2024-06-01 15:22:31"))))
'''root = lisp.ParseLisp(text)# 遍历节点
for status in root['status']:# 在节点下按照参数顺序遍历timestamp = status[0][0]# 获取节点下的一级子节点timestamp_string = '-'.join(child.name for child in timestamp.children)print('Timestamp:', timestamp_string)version = status[0][2][1]# 判断节点名称assert version == 'version'# 获取移除引号的节点名称print('Version:', version[0].stripname)