Python Rule System

1. 安装lark-parser

$ pip install lark-parser

2. 使用

$ python3 demo.py

2.1 自定义Grammar

grammar = """
?start: "if" logit "then" value "else" value -> assign

?value: "true" -> true
 | "false" -> false
 | string

?logit: and
 | variable -> variable_self
 | "!"variable -> not_variable_self
 | variable ">" NUMBER -> bigger
 ...

?and: atom
 | logit "and" logit -> and_op
 | logit "or" logit -> or_op

?atom: "(" logit ")"

string : ESCAPED_STRING -> string

variable: "@"NAME | "@"string -> variable

%import common.CNAME -> NAME
%import common.ESCAPED_STRING
%import common.NUMBER
%import common.WS
%ignore WS
"""

2.2 定义/解析规则

from rule.rule import init_grammar_parser
# 定义规则:买5个包子回来,如果看到西瓜并且西瓜重量大于或等于10,买1个
rule = """
if
("西瓜" in @"物品列表" and @"西瓜重量" >= 10)
then "买1个包子" else "买5个包子"
"""
# 构建grammar parser
parser = init_grammar_parser()
# 将规则解析为语法树
tree = parser.parse(rule)
print(tree.pretty())

assign
 and_op
 exist_in
 string	"西瓜"
 variable
 string	"物品列表"
 bigger_equal
 variable
 string	"西瓜重量"
 10
 string	"买1个包子"
 string	"买5个包子"

2.3 匹配规则

from rule.rule import EvalTree
variable_dict = {
 "西瓜重量": 10,
 "物品列表": {"包子", "西瓜", "香蕉"},
}
tree_evaluator = EvalTree()
rule_result = tree_evaluator.transform_tree(tree, variable_dict)
print(rule_result) # 买1个包子

3. 参考