python - 如何匹配 pyPEG 中的无序事物？

Question

我有以下文件:

orange
apple
orange
apple
apple 
lime
banana

每种水果都有一个与之匹配的类:

class Banana:
    grammar = ....

class Apple:
    ...

我必须无序地匹配每个水果，我无法预先告诉顺序是什么。如何设置 FruitBasket 语法来匹配它们？

class FruitBasket:
    grammar = ?????

ps:水果其实是复杂的规则，每种水果类型代表不同的代码块，比如函数、原型(prototype)、全局变量等。

Answer 1

使用 list :

A list instance which is not derived from pypeg2.Concat represents different options. They're tested in their sequence. The first option which parses is chosen, the others are not tested any more. If none matches, a SyntaxError is raised.

例如:

from pypeg2 import K, List, maybe_some, parse

class Apple:
    grammar = K('apple')

class Banana:
    grammar = K('banana')

class Lime:
    grammar = K('lime')

class Orange:
    grammar = K('orange')

class FruitBasket(List):
    '''An unordered collection of zero or more fruits'''
    grammar = maybe_some([Apple, Banana, Lime, Orange])


if __name__ == '__main__':

    fruit = '''
        orange
        apple
        orange
        apple
        apple 
        lime
        banana
    '''

    print(parse(fruit, FruitBasket))

输出:

FruitBasket([<__main__.Orange object at 0x7ffa4991d8d0>, <__main__.Apple object at 0x7ffa49922c18>, <__main__.Orange object at 0x7ffa49927a58>, <__main__.Apple object at 0x7ffa499279b0>, <__main__.Apple object at 0x7ffa49927908>, <__main__.Lime object at 0x7ffa421ad828>, <__main__.Banana object at 0x7ffa421ad8d0>])