Python 根据前面的结果选择解析器
我正在分析几个输出,这些文件有两个不同的头:Python 根据前面的结果选择解析器,python,haskell,pyparsing,parsec,Python,Haskell,Pyparsing,Parsec,我正在分析几个输出,这些文件有两个不同的头: header1 = " MO EIGENVALUES, MO OCCUPATION NUMBERS, AND CARTESIAN MO EIGENVECTORS AFTER SCF STEP -1" header2 = "MO EIGENVALUES, MO OCCUPATION NUMBERS, AND SPHERICAL MO EIGENVECTORS AFTER SCF STEP -1" 基于结果是笛卡尔坐标系或球坐标系的语句,我想应用相
header1 = " MO EIGENVALUES, MO OCCUPATION NUMBERS, AND CARTESIAN MO EIGENVECTORS AFTER SCF STEP -1"
header2 = "MO EIGENVALUES, MO OCCUPATION NUMBERS, AND SPHERICAL MO EIGENVECTORS AFTER SCF STEP -1"
基于结果是笛卡尔坐标系或球坐标系的语句,我想应用相应的解析器
在Haskell中,我可以编写一个解析器,根据前面的结果决定下一步要做什么,如下所示:
myparser = do
xs <- someParser
if xs == "foo"
then parser1
else parser2
myparser=do
xs这里是一个应该有效的解决方案的概要。其思想是实现一个新的解析器类,该类运行一个解析器,并根据返回的令牌在两个备选方案之间进行选择
# modeled after class And in pyparsing.py
class IfThenElse(ParseExpression):
def __init__(self, exprs, savelist = True):
super(IfThenElse,self).__init__(exprs, savelist)
self.parserIf = exprs[1] # maybe exprs[0]?
self.parserThen = exprs[2]
self.parserElse = exprs[3]
self.mayReturnEmpty = all(e.mayReturnEmpty for e in exprs[2:])
self.setWhitespaceChars( ... )
self.skipWhitespace = self.exprs[0].skipWhitespace
def parseImpl(self, instring, loc, doActions = True):
loc, toks = self.parserIf._parse(instring, loc, doActions)
if ...toks...:
loc, toks2 = self.parserThen._parse(instring, loc, doActions)
else:
loc, toks2 = self.parserElse._parse(instring, loc, doActions)
return loc, toks2 # maybe combine toks and toks2?
def __str__(self):
return "blah" # for now
if…toks…
是您放置切换逻辑的地方
您还需要实现一个\uuuu str\uuu
方法,可能还需要实现一个checkRecursion
方法
有一些细节需要弄清楚。。。也许exprs[0]
是“if”解析器,而不是exprs[1]
用IfThenElse(p,q,r)
实例化这个解析器——应该与和解析器具有相同的语法。我认为在pyparsing中,一个人只需写:
oneParserToRuleThemAll = header1 + parser1 | header2 + parser2
如果标题行与'header1'匹配,则pyparsing将继续进行,并使用parser1进行其余的解析。否则,它将尝试匹配“header2”,如果匹配,将使用parser2
使用动态解析器元素和解析操作肯定可以获得更多的异国情调。看起来是这样的:
foo_parser = ...
bar_parser = ...
variable_parser = Forward()
switch_parser = Literal("foo") | Literal("bar")
def select_variable_parser(tokens):
if tokens[0] == "foo":
variable_parser <<= foo_parser
if tokens[0] == "bar":
varaible_parser <<= bar_parser
switch_parser.setParseAction(select_variable_parser)
parser = switch_parser + variable_parser
有趣的扩展,有点像三元运算符类。
parser = "foo" + foo_parser | "bar" + bar_parser