区分 pyparsing 中的匹配

我想用 pyparsing 解析一些单词和一些数字。简单就对了。

from pyparsing import *

A = Word(nums).setResultsName('A')
B = Word(alphas).setResultsName('B')
expr = OneOrMore(A | B)

result = expr.parseString("123 abc 456 7 d")
print result

上面的代码打印['123', 'abc', '456', '7', 'd']。所以一切都有效。现在我想对这些解析值进行一些处理。对于这个任务，我需要知道它们是否匹配A or B。有没有办法区分这两者。

经过一番研究后我发现的唯一一件事是items的方法ParseResults班级。但它只返回[('A', '7'), ('B', 'd')]，只有最后两场比赛。

我的计划/目标如下：

for elem in result:
    if elem.is_of_type('A'):
        # do stuff
    elif elem.is_of_type('B'):
        # do something else

我如何区分A and B?

getName() 做得很好。您还可以使用标记显式装饰返回的标记，指示进行了哪个匹配：

def makeDecoratingParseAction(marker):
    def parse_action_impl(s,l,t):
        return (marker, t[0])
    return parse_action_impl

A = Word(nums).setParseAction(makeDecoratingParseAction("A"))
B = Word(alphas).setParseAction(makeDecoratingParseAction("B"))
expr = OneOrMore(A | B)

result = expr.parseString("123 abc 456 7 d")
print result.asList()

Gives:

[('A', '123'), ('B', 'abc'), ('A', '456'), ('A', '7'), ('B', 'd')]

现在您可以迭代返回的元组，并且每个元组都标有适当的标记。

您可以更进一步，使用类来捕获类型和特定于类型的解析后逻辑，然后将该类作为表达式的解析操作传递。这将在返回的 ParseResults 中创建类的实例，然后您可以使用某种方法直接执行该实例exec or doIt method:

class ResultsHandler(object):
    """Define base class to initialize location and tokens.
       Call subclass-specific post_init() if one is defined."""
    def __init__(self, s,locn,tokens):
        self.locn = locn
        self.tokens = tokens
        if hasattr(self, "post_init"):
            self.post_init()

class AHandler(ResultsHandler):
    """Handler for A expressions, which contain a numeric string."""
    def post_init(self):
        self.int_value = int(self.tokens[0])
        self.odd_even = ("EVEN","ODD")[self.int_value % 2]
    def doIt(self):
        print "An A-Type was found at %d with value %d, which is an %s number" % (
                self.locn, self.int_value, self.odd_even)

class BHandler(ResultsHandler):
    """Handler for B expressions, which contain an alphabetic string."""
    def post_init(self):
        self.string = self.tokens[0]
        self.vowels_count = sum(self.string.lower().count(c) for c in "aeiou")
    def doIt(self):
        print "A B-Type was found at %d with value %s, and contains %d vowels" % (
                self.locn, self.string, self.vowels_count)


# pass expression-specific handler classes as parse actions
A = Word(nums).setParseAction(AHandler)
B = Word(alphas).setParseAction(BHandler)
expr = OneOrMore(A | B)

# parse string and run handlers
result = expr.parseString("123 abc 456 7 d")
for handler in result:
    handler.doIt()

Prints:

An A-Type was found at 0 with value 123, which is an ODD number
A B-Type was found at 4 with value abc, and contains 1 vowels
An A-Type was found at 8 with value 456, which is an EVEN number
An A-Type was found at 12 with value 7, which is an ODD number
A B-Type was found at 14 with value d, and contains 0 vowels