rply 0.7.8

欢迎使用RPLY！这是一个纯Python解析器生成器，也适用于RPython。它是David Beazley的出色PLY的直接移植，具有新的公共API和RPython支持。

您可以在线上找到文档。

基本API

from rply import ParserGenerator, LexerGenerator
from rply.token import BaseBox

lg = LexerGenerator()
# Add takes a rule name, and a regular expression that defines the rule.
lg.add("PLUS", r"\+")
lg.add("MINUS", r"-")
lg.add("NUMBER", r"\d+")

lg.ignore(r"\s+")

# This is a list of the token names. precedence is an optional list of
# tuples which specifies order of operation for avoiding ambiguity.
# precedence must be one of "left", "right", "nonassoc".
# cache_id is an optional string which specifies an ID to use for
# caching. It should *always* be safe to use caching,
# RPly will automatically detect when your grammar is
# changed and refresh the cache for you.
pg = ParserGenerator(["NUMBER", "PLUS", "MINUS"],
        precedence=[("left", ['PLUS', 'MINUS'])], cache_id="myparser")

@pg.production("main : expr")
def main(p):
    # p is a list, of each of the pieces on the right hand side of the
    # grammar rule
    return p[0]

@pg.production("expr : expr PLUS expr")
@pg.production("expr : expr MINUS expr")
def expr_op(p):
    lhs = p[0].getint()
    rhs = p[2].getint()
    if p[1].gettokentype() == "PLUS":
        return BoxInt(lhs + rhs)
    elif p[1].gettokentype() == "MINUS":
        return BoxInt(lhs - rhs)
    else:
        raise AssertionError("This is impossible, abort the time machine!")

@pg.production("expr : NUMBER")
def expr_num(p):
    return BoxInt(int(p[0].getstr()))

lexer = lg.build()
parser = pg.build()

class BoxInt(BaseBox):
    def __init__(self, value):
        self.value = value

    def getint(self):
        return self.value

然后您可以这样做

parser.parse(lexer.lex("1 + 3 - 2+12-32"))

您也可以替换自己的词法分析器。词法分析器是一个具有next()方法的对象，它返回序列中的下一个令牌，或者如果令牌流已耗尽，则返回None。

pg = ParserGenerator(...)

@pg.error
def error_handler(token):
    raise ValueError("Ran into a %s where it wasn't expected" % token.gettokentype())